Hello and welcome Clint,
As far as the article, the first part is about the relationship to cancer. While BW may have brought this up, the Baha'i Writings do not assert (nor deny) any kind of link to it, so this is not very relevant I think. And Baha'is, indeed should not feel that our Faith calls them to make assertions that are not supported by our Writings or by science just because something is forbidden in our Faith (not saying BW was doing that, just saying).
Also to your point on the dual nature of "drugs", the Qur'an indicates that alcohol--another substance which is forbidden to Baha'is unless prescribed by a physician--even has advantages, though it indicates that these are less than the disadvantages and another later verse more explicitly prohibits it:
"They will ask thee concerning wine and games of chance. SAY: In both is great sin, and advantage also, to men; but their sin is greater than their advantage."
(Qur'an 2:215, Rodwell translation)
So, on adjudging the link to cancer, Baha'is interested in the topic can examine the scientific evidence (though again, a negative answer would not change the fact that it is prohibited to Baha'is).
The article then goes on to assert, "even if marijuana IS dangerous, prohibition makes marijuana more dangerous". On this point, I think the Baha'i Writings cannot be seen as being definitely in agreement or in disagreement (and the answer might also vary by country and by time).
As per http://bahai9.com/wiki/Prohibition_and_drug_wars
, violence and force is reluctantly permitted for ridding the world of (non-medicinally-prescribed) opiates. That might perhaps be seen as indicating that a drug war on non-opiates might be unjustified. However, the other quotation on this page indicates that, the prohibition of alcohol might be something Baha'is would welcome--except with the critical caveat that it would depend--by country--on the "exact conditions as to whether by force of legislation people can be stopped from drinking". Since Baha'is do not get involved in politics, I think an assessment of this latter question would only be of relevance:
1) To individual Baha'is PRIVATELY wishing to determine whether a political candidate espousing or opposing legalization was following a reasonable agenda.
2) To the Universal House of Justice in the distant future which Baha'is believe, after a supremely voluntary and democratic process, will eventually be accepted by the majority of peoples as its legislative head.
Baha'u'llah indicates in the Most Holy Book of the Baha'i Faith:
"Gambling and the use of opium have been forbidden unto you. Eschew them both, O people, and be not of those who transgress. Beware of using any substance that induceth sluggishness and torpor in the human temple and inflicteth harm upon the body. We, verily, desire for you naught save what shall profit you, and to this bear witness all created things, had ye but ears to hear."
(Kitab-i-Aqdas, paragraph 155
The Notes to the Kitab-i-Aqdas were prepared under the supervision of the Universal House of Justice, the institution ordained by Baha'u'llah in the same book, and which His Son and designated Successor indicates will be "freed from all error", mentions that other derivatives of cannabis fall under this prohibition. So from a question of whether the Baha'i Writings accept it or not, there is really nothing further to discuss--they don't.
The article you mentioned (and your assertion that it is "completely safe") deals very little with research about "sluggishness and torpor in the human temple" or other "harm upon the body" (e.g., on memory). Another important consideration for the Baha'i Writings--which I think distinguishes smoking nicotine (which is "only" very strongly discouraged) from other drugs, is whether something impairs one's moral or intellectual judgment. Morality, and how we treat other people, is of preeminent importance to Baha'is, so avoiding anything which may impair our ability to do so, is a strong consideration. And just because drugs may have certain benefits like relaxation does not of course mean that there are other, less harmful ways, to obtain the same benefits.
As far as independent investigation of truth and an "open mind", if the already-mentioned quotations on prohibition were not enough, we can address a little more of how the Baha'i Writings actually interpret this general principle of independent investigation, and not how it is popularly (mis)understood.
An analogy is given in the Baha'i Writings of accepting the advice of a doctor. While not putting on full blinders (one must use one's judgment, of course, to determine whether the physician is competent enough in the first place, how much more so for deciding to entrust oneself to One making the claim to be a perfect Manifestation of God for all to obey), one recognizes that his learning is superior to one's own, so while it is natural to seek for additional opinions, to research oneself on the internet, etc., one cannot lightly dismiss a physician's prescription just because one does not like the taste of the medicine, or the trouble required to adhere to a regimen, etc. He or she is the competent one we sought for advice in the first place, so it makes no sense to dismiss their recommendations out of hand.
Baha'u'llah, in His work, the Seven Valleys, addressed to a mystic, indicates the flaw in relying solely on reason:
"For some hold to reason and deny whatever the reason comprehendeth not, and yet weak minds can never grasp the matters which we have related, but only the Supreme, Divine Intelligence can comprehend them:
How can feeble reason encompass the Qur'án,
Or the spider snare a phoenix in his web?"
'Abdu'l-Baha elaborates on this, indicating the fallibility of our senses, reason, intuition, and yes, interpretation of scripture (of which OUR understanding is also based on reason).
In other words, independent investigation does not allow for any person to judge things independently of God's own perfect Educator! What would be the purpose of the religion if each person were to discard its logic in favor of their own?
As far as restriction of drugs to usage where prescribed by a medical professional, it is true indeed that even medical professionals are only human. And when speaking of the general need to adhere to the advice of medical professionals, the Baha'i Writings do allow for exceptions or qualifications (e.g., recognizing that psychiatry was in its infancy) and offer advice for seeking a second opinion in the case of a surgery, etc..
But the fact remains that with such loaded and controversial issues as this, we are fortunate to be protected by a wiser Physician which is ahead of the times and has indicated unequivocally that it is normally forbidden. There are no mothers adhering to Baha'i law who jeopardize their children with addictions (yes, marijuana can be addictive; I know someone personally who faced this); there are no accidents or debasement of character, brought on by the clouding of judgment caused by drugs. A TRULY independent investigation will no doubt lead to the same conclusion as the Baha'i Writings.
As far as your statement that it is naive and ignorant to leave matters in doctor's hands (even though again one can seek additional opinions as a Baha'i), I would maintain that one could also say that it is naive and ignorant to leave one's fate in the hands of those seeking reckless abandon and unqualified justification for their actions. You can see the predisposition of no shortage of advocates of marijuana failing to acknowledge anything negative whatsoever about it--attacking anything contrary to their position with their own blind dogmatic fervor.
As far as your statement, "psychedelic substances have existed for many thousands of years, and humans have used psychedelic substances to their benefit long before bahai or any other religion existed," (assuming your point is true that they were used before any religion existed) this is of no relevance to the question of whether it is harmful or not. Polygamy and slavery existed for thousands of years, perhaps even also with some negligible benefits, but this cannot justify them to a rationally-minded person.
clint wrote:"long before politics began a propaganda war demonising these healing and beneficial substances..."
...governments and media feed populations with propaganda and discourse relating to "drugs", they want you to think that "drugs" are bad, they do not want you to think for yourself, they do not want you to have an open mind. consider this, governments declare war on people of other countries, many wars still exist today, think of all the destruction to the land and think about all the suffering to humanity as a result of this... this is the same government telling you "drugs" are bad. consider the media, constantly promoting an unhealthy lifestyle of meaningless consumerism, influencing children from a young age on what to think, how to dress, what to buy... this is the same media that tells you "drugs" are bad.
Propaganda is something which is not only employed by governments (who can hardly be portrayed as some black-and-white villainous monster out to get us and take away all our freedoms, even with its sometime admitted faults). It is also employed by those who wish to pull out all restraints on behavior and justify and enable their own self-and-other-destructive actions.
The media--at least in the U.S. where I'm from--is hardly giving an unqualified rejection of drugs. Nowadays, anti-authority and pleasure-seeking sentiments seem so strong that it is only acceptable to joke in favor of drugs. This propaganda, while not part of some sinister plot, is even more harmful, as the Baha'i Writings also indicate:
"Such a chaste and holy life, with its implications of modesty, purity, temperance, decency, and clean-mindedness, involves no less than the exercise of moderation in all that pertains to dress, language, amusements, and all artistic and literary avocations. It demands daily vigilance in the control of one's carnal desires and corrupt inclinations. It calls for the abandonment of a frivolous conduct, with its excessive attachment to trivial and often misdirected pleasures. It requires total abstinence from all alcoholic drinks, from opium, and from similar habit-forming drugs."
(Shoghi Effendi, Advent of Divine Justice, p. 30)
"The Bahá'í standard is very high, more particularly when compared with the thoroughly rotten morals of the present world. But this standard of ours will produce healthier, happier, nobler people..."
(From a letter dated 19 October 1947 written on behalf of Shoghi Effendi to an individual believer)
As far as entheogens, the Universal House of Justice has indicated:
"Anyone involved in the use of peyote should be told that in the Bahá'í Faith spiritual stimulation comes from turning one's heart to Bahá'u'lláh and not through any physical means. They should therefore be encouraged to give up the use of peyote."
(From a letter of the Universal House of Justice to the National Spiritual Assembly of the United States, November 9, 1963: Alaska Bahá'í News, May 1972, p. 4, in Lights of Guidance, no. 1185)
"Concerning the so-called "spiritual" virtues of the hallucinogens, ... spiritual stimulation should come from turning one's heart to Bahá'u'lláh, and not through physical means such as drugs and agents."
(From a letter dated 15 April 1965 written by the Universal House of Justice to the National Spiritual Assembly of the United States, Chaste and Holy Life, A, no. 28)
As far as liberation, Baha'u'llah summarized our attitude toward the dialectic of liberation/liberty and humble submission:
Consider the pettiness of men's minds. They ask for that which injureth them, and cast away the thing that profiteth them. They are, indeed, of those that are far astray. We find some men desiring liberty, and priding themselves therein. Such men are in the depths of ignorance.
Liberty must, in the end, lead to sedition, whose flames none can quench. Thus warneth you He Who is the Reckoner, the All-Knowing. Know ye that the embodiment of liberty and its symbol is the animal. That which beseemeth man is submission unto such restraints as will protect him from his own ignorance, and guard him against the harm of the mischief-maker. Liberty causeth man to overstep the bounds of propriety, and to infringe on the dignity of his station. It debaseth him to the level of extreme depravity and wickedness.
Regard men as a flock of sheep that need a shepherd for their protection. This, verily, is the truth, the certain truth. We approve of liberty in certain circumstances, and refuse to sanction it in others. We, verily, are the All-Knowing.
Say: True liberty consisteth in man's submission unto My commandments, little as ye know it. Were men to observe that which We have sent down unto them from the Heaven of Revelation, they would, of a certainty, attain unto perfect liberty. Happy is the man that hath apprehended the Purpose of God in whatever He hath revealed from the Heaven of His Will that pervadeth all created things. Say: The liberty that profiteth you is to be found nowhere except in complete servitude unto God, the Eternal Truth. Whoso hath tasted of its sweetness will refuse to barter it for all the dominion of earth and heaven.
(Baha'u'llah, Kitab-i-Aqdas, pars. 122-125)
Of course, it is up to each individual to decide this for themselves. But while you are free to question the legitimacy of the Baha'i Faith itself, there is no ambiguity in the Baha'i Teachings on this matter--they clearly oppose marijuana use, to the point of apparently even allowing an individual to face the strong action (strong in spiritual terms) of losing their administrative rights for flagrant usage (though I am basing this latter point only on the fact that fragrant alcohol usage can be subject to this sanction as can other "immorality").