An extension of the argument you put forward is to legalise all narcotics. I wish I could be sure that you would baulk at such an idea.
Well, I do. All substances should be legally available. Who is the government to tell me what I am allowed to shoot/smoke/sniff? I'm mature and the only one who is responsible for me.
Besides that, the criminilization of drugs leads to all the known consequences, like overcrowded jails, courts & police not able to follow important cases because of overload, etc.
I know I am pretty alone with this opinion. In discussions with friends/family I always earn irritated glances when I say "Solving the drug problem? Legalise everything.".