Should marijuana be legalized for recreational purposes

The only valid point prohibitionists can make is to claim that other people's drug use can somehow affect them in a negative way. It's unfortunate and embarrassing for them that they can't seem to come up with something that doesn't involve subsequent actions (like driving or stealing) or health costs to taxpayers which are no different than what a steady diet of McDonald's incurs. They can't prove that someone's drug use might lead to subsequent harmful actions to others because no credible medical authority has ever produced a study which suggests that drug use alone compels users to commit other crimes. And they can't complain about health costs unless they want to ban McDee's for the same reason or be a hypocrite.

Regarding prohibition as a whole, whether it's alcohol or drugs: history doesn't repeat itself, people just repeat the same mistakes.