At university two of my friends went down a dark road with Marijuana use. One destroyed his very bright future - went from a top student to a dropout. The other one had severe mental psychosis episodes, the last one being where he physically threatened other students with a knife and was arrested and subsequently medically repatriated back to his home country - his parents were financially ruined by the cost of getting him home.

I am not sure that this is as black and white as some people make it out to be. Complete freedom to do whatever one pleases is not Utopia. There is a limit if one wants a functioning society that is on the whole safe and high trust.