This is not how a free society operates. I choose what I put into my body and not you or anyone else. If doing so causes me to commit a crime, then punish that crime, but banning drugs because "most people" don't like them is not freedom. If you don't like them, then don't do them.
>Is it even possible to be a responsible Heroin user?
A free person should be given the opportunity to demonstrate their responsibility instead of it being assumed such responsibility is not possible simply because a majority of the populace finds a substance distasteful.