I am a libertarian and I don't use drugs, but I recognize a slippery slope when I see one. When a person's actions hurt another person, punish him. But, please, LEAVE ME ALONE! The individual is being legislated out of existence.
You recognize a "slippery slope" when you see one? Good. Recognize this one.
Whatever bad consequences you believe come from interdicting drugs pales in comparison to the bad consequences which come from not interdicting drugs.