People should have the right to decide what they do and don't put into their body, provided that they are properly capable of responsible judgement... i.e. not a child, seriously mentally ill, etc. So long as someone isn't harming anyone else, I see no good reason why they can't use drugs. Although of course, if you put a load of aggressive youths on large amounts of coke, you're just asking for a fight to start, so there needs to be some kind of balance.
I'd say that overall, some drugs that are highly addictive and harmful, like heroin and meth, just aren't worth it in the long run for anyone and cause too much damage. Whereas drugs like tobacco, marijuana, even speed, can be used in moderation and not usually seriously affect a user in their normal life. I mean, have you ever seen a less
violent person than one who's stoned?
If everyone smoked pot, there'd be no war