i am sorry that you would let a good friend screw up his life with drugs and not get involved in saving that person's life.
there are two problems with your argument: first, the person who screws up his life will become another government dependent. secondly, before he has screwed up his life, he has the potential to screw up someone else's life while he is high on drugs. lawyers making poor decisions, doctors who accidently slice an artery, rail switch operators who cannot keep track of what direction the trains are going on any one track.
it is people that want freedom, but who do not want the responsibility that comes with their freedom that are a bane to society.
That is the libertarian message, in a nutshell. Without responsibility, there can be no liberty. Without liberty, there can be no morality. It's that second statement that drug warriors have such a hard time with.