This is certainly true to some extent. After all, millions upon millions get intoxicated legally on alcohol daily, and a certain percentage of those are habitual drunks, all of which has an impact on society. The prohibition era proved only one thing, that criminalizing intoxicants does not lead to considerably less intoxication, it just moves it underground and fuels black markets. Following this logic, black markets have to operate under organization, and will profit greatly from these actions. Hence, you create an environment for common criminals to become very powerful and wealthy, and a great drive towards protecting their little empires. Caustically, it also creates larger and less democratic police and judicial actions as a reactive process, which harms freedoms significantly. These processes in our judicial and police systems are accumulative in nature, so that even if the problems lessened (in the prohibition example; liquor traffickers), the increased tax burden and intrusion upon freedoms will not collaterally lessen.
In summary, the criminalization of intoxicants has proven ineffective in actually stopping the intake of these substances, and primarily serves very negative results at multiple levels. Ignoring the question of morality (after all, none of us are profoundly authoritative on what is truly good or evil), our actions have harmed society at large, to the benefit of a select few. Returning to the original reason for this response, you are quite correct in observing that someone choosing that kind of lifestyle quite often does do great harm to themselves, and even others on occassion. My preferred solution is not the path of criminalization, but federalization and transitioning the approach to a question of health care. After all, if we send an addict to prison and ruin his life with a felony/etc for possession, we are almost certainly going to create an actual motivated criminal who may transition to theft or assault after going through criminal school 101, vs. the path of rehabilitation options, counter-agent medications (which make it impossible to achieve a "high"), as well as pathways to job training and/or faith-based programs.
Are these solutions perfect? Hardly. I maintain that they remain far more appealing than wasting countless billions of dollars for decade after decade down a path that has only produced destruction and lined the pockets of the corrupt.
