During the prohibition, people risked being blind from an inept stiller who produced methanol instead of ethanol.
With alcohol legalized, how many cases do you hear about people going blind from illegally run stills?
There will probably always be illegal drugs, but at least by regulating them we can ensure that minimum harm is done.
It would also free up resources to go after the worst of it, which should drive the costs of these drugs to unaffordable levels.
So, in addition to alcohol, what other drugs would you add to the "legal" list?