To be clear, I really did not say that to offend anyone. And of course I would never try to tell anyone what they can and cannot do. All I stated is what a person should and should not do for his own sake (which just so happens to be in the better interest of most everyone else too, but the point is it's for your own happiness). And in my conviction (not opinion. I believe it is a fact) if you're doing drugs for non-medical reasons, you are hurting yourself. Doesn't mean I hate you, it just means I think you are doing something objectively destructive.
If you really want me to tell you my logic in believing this fact, I could of course, but I think your question was rhetorical.