The fact that people enjoy doing it and the only person they harm while doing it is themselves should be enough.
I... guess, in a way, I am haha. It's really kinda contradictory to my personality and my lifestyle (as you probably already know tbh!) but yeah I suppose I just feel like it's a safer and healthier world for people that way, even if it is a bit like living in a large padded room. I guess our difference in opinions is just due to our opposite views on the legalisation or illegalisation (is that even a word?) of stuff.
However, I really like your idea of education of the risks. I feel like a lot of people, honestly possibly including me, are a bit fuzzy on the risks of marijuana. We're all taught about what cigarettes can do to you, possibly what alcohol can do to you, but its legal status makes marijuana and other drugs a bit taboo in education, from what I've seen. Legal or not I'd totally like to see further, unbiased, education there.