This is like saying people ought to be free to sell meth on the corner because you are smart enough to avoid addiction. Societies have good reason to ban things that are a net negative to society.
There is an argument for decriminalizing drug possession. The same argument in no way holds for drug dealing. The price would come down and availability would skyrocket as would the problems that stem from use.
I don't do them but have respect to one's own opinion about their own body even if that means poisoning/killing themselves.