Would you trust a scientist? Quite apart from whether he is honest or not; is his opinion worth anything? I suppose, in this day and age when actors, pop-singers and sports stars are supposed to have the last word on everything, you might think that a scientist is a bit of an improvement.
The correct answer is, "If he knows what he's talking about." And for the purpose of this article so I don't have to keep writing his/her, let's assume that the male embraces the female.
I have always prided myself on reading widely and picking up scraps of information from many different places. However, if you got me on astrophysics then my opinion would be worth no more than that of Tiger Woods. On CLL though, I could wipe the floor with Stephen Hawking.
Even on CLL it is possible to disagree. Michael Keating and I, though agreeing on many things, had a fierce debate on one aspect of CLL on which we disagreed.
The best committee that I ever sat on was chaired by a non-specialist who had no detailed knowledge of the subject under consideration. He allowed debate to flow.
Scientists as a group dig very deep and narrow holes. They often know an awful lot about very little. Politicians, on the other hand, skim the surface from a large area. They can't be expected to know a subject deeply, but, if they are honest, they will look at a topic fairly and seek expert help over detail.
To go back to the topic of drugs. A complete libertarian would say that if someone wants to take a drug that harms his own body the let him; it is his, and only his, responsibility. On the other hand, if he has the same health insurance as I do, why should my premiums go up just because he indulges himself?
However, many drugs cause harm to the community. Alcoholics, apart from raising my insurance premium, beat their wives, cause motor car accidents, vomit in the streets, desert their children, reduce their families to penury and can't work properly. So what? Banning alcohol does not work; we saw how much harm it did during Prohibition. It just leads to an increase in criminal behavior. Look at it another way; legalizing it hasn't worked either. We still have wife-beatings, car accidents and poverty.
Scientists may tell us that cannabis is less harmful than tobacco and alcohol. How do they know? At first glance cigarette smoking seemed an attractive proposition. Actors, singers and sports stars endorsed the product. Even doctors agreed. Given, it did make your clothes stink, but it helped your cough, didn't it? Then in 1951, Richard Doll demonstrated that smoking caused lung cancer. The evidence was convincing enough to make him stop smoking. Nevertheless, it took many years before anybody believed him and many more before everybody believed him. Such convincing evidence is hard to obtain. There are no such studies for cannabis or ecstasy. People lie - either because of guilt of bravado - about their drug taking. How would you isolate the effect of one drug compared to another?
Cannabis apparently induces a degree of intoxication. How long after smoking a joint is it safe to drive? If you were stopped, what test would the policeman use to determine whether you were safe to drive? Supposing you had popped an 'E' and later on smoked some pot. Are you safe to fly your aeroplane tomorrow? A scientist who has opinion on such a thing had better couch it in conditional clauses if he doesn't want to be sued.
If the question is a simpler one such as, "Do cannabis users develop schizophrenia more commonly than non-users?" then the answer is yes, but asked how commonly, a wise scientist will demur. Remember the guy who won the Nobel Prize for inventing the transistor? This was a proper Nobel Prize; not like the Mickey Mouse ones they gave to Gore and Obama. Well, he turned out to espouse the discredited science of Eugenics, and even started a sperm bank for geniuses. Do you want to be ruled by scientists? I don't. There is a quote from the New Testament where Festus, the Roman governor says to the Apostle Paul, "Your great learning is driving you insane!" We would be insane to be ruled by scientists.