This much is clear. Scheduling MJ is extremely unwise. But I would also extend this to everything in the psychedelic / hallucinogenic category. They do no psychological harm and an increasing body of evidence indicates that they, in all likelihood, do a significant amount of mental good for responsible users.
An acute example of this is a psychedelic called “DMT”. This psychedelic is nearly everywhere in nature, including our own brains. When inhaled, it lasts less than 10 minutes, give or take. After that 10 minutes, a user is completely sober without any indication that they were not, and no physiological side effects. But during that 10 minutes? It is an acute spiritual and existential experience, possibly the most acute non-normal experience possible for a human being. A true exploration of altered states, and possible contact with a different form of life unbound from our reality.
And for some reason, this substance is scheduled. It does no harm to a user, to third parties, nor to society, is short lived, and offers true spiritual experience but it’s scheduled. The scheduling as a whole is archaic, oppressive, and if nothing else, misguided.
This is also in top of the fact that it discourages addicts from seeking real treatment due to fear of being criminalized.