Why does this Harvard professor say to legalize all drugs?

Prohibition causes drug trafficking to go underground.  It increases crime and corruption involved in the market.  Pushing it underground has compromised quality control.; it's unregulated and you don't know what you're actually getting.

Drug use is not going away, in fact, it's a huge part of society.  From caffeine to nicotine to alcohol, the human race is partly driven by the concoction of chemicals available to us.  Often, in mediative doses, they greatly enhance our learning capability and sense of well being.

This is why economist, Jeffrey Miron, predicts that legalizing and treating all drugs with the same respect we have for the aforementioned nicotine, caffeine and alcohol can greatly improve quality of life for the race as a whole.  Prohibition landed millions of people in jail but with public education comes a passage of fear and clear minds to make good decisions.