Earlier quoted context omitted.
With legalization, the drugs would be cleaner and dosing more predictable. We could then focus on helping addicts recover instead of worrying about the legal trouble and violence they might bring to our homes if we try to help them.
So far legalization has not proven to solve the problems of demand or addiction. In the past several years legally available drugs have been the most abused and resulted in significant problems. I am not claiming this as a justification for increased enforcement either. If you aren't solving for demand you either aren't taking the problem seriously or you have anterior motives to ending drug abuse.
The point of legalization is to solve the problems of having a massive black market for drugs. Getting people to quit using drugs is a different issue entirely.