Doesn't that mean we should also shut down casinos, for example?
I don't think the answer has ever been "make it so people can't buy the stuff", because that can't work. Instead, I believe that education, quality control, and help towards addicts would work much better.
Education, quality control and help towards addicts implies the need for regulation and taxation of profits. For instance, gambling and casinos tend to be permitted but tightly controlled by law in many countries, for exactly this reason. An entirely anonymous market will have trouble enabling regulation and taxation to offset the damage done.
I don't think the answer has ever been "make it so people can't buy the stuff", because that can't work. Instead, I believe that education, quality control, and help towards addicts would work much better.