Well I personally don't see anything wrong with marijuana, it's just a cigarette with a little extra something. Possibly ecstasy as well, but then again I don't know much about it.
As for things such as heroin...as much as I am person to let people do what they want cause it's their life, that shit has some serious reprecussions, like people turning to theft to be able to afford purchasing it. I don't know if the answer is keeping them illegal or just making it legal but highly regulated, but I don't think dangerous substances like that should be legal and free.
Course I don't do any of them. I just don't see myself enjoying the feelings they would give me. I don't really care if others do some of the lighter stuff, everyone needs a little something to get through the day, which can be certain drugs, excersise, food, alcohol, movies, music, something, though I don't really want to deal with your ass whenever your high/drunk. The heavier stuff...yeah, no. You're slowly killing yourself in a horrible, horrible way, I don't want to have to either fight with you to get you off it or watch as you deteroriate and die.