I don't think this really addresses the point though. Alcohol is sold with known purity, quality, and quantity. You aren't going to overdose due to an impurity.

Yet dangerous drinking is still very common, and alcohol causes significant strains on our society, perhaps more than any other drug. Why do we think that the situation would be different with legalizing other drugs? A major decline in the risk per use massively outweighed by a huge increase in use over time due to legalization.