[Xenalyte]

Just that it is harmful if used habitually and/or in unsafe situations

Does your argument hinge on the "habitually" part? If so, I can present empirical and anecdotal evidence to the contrary. Every stoner I know has (at the least) a good job. One of my pothead buddies owns her own company. Another is what you'd call a managing director, if he were at a larger company. Two more are seventh- or eighth-year attorneys with firms whose names are recognized nationwide.

The point is that some habitual potheads, like some habitual drunks or smokers (as if there's any other kind of smoker), are as productive as non-potheads - in some cases, including mine, quite a bit more productive. (The corollary, of course, is that some aren't.)