Banning pot wasn't about drugs. "It was about power", -- as libertarians put it. -- And as you hypocritically put it about DDT.
Yeah, just think of the millions of lives that could have been saved if only pot wasn't banned.
Do you really think putting millions of people in prison for pot over the last 40 years hasn't ruined more than a few lives?
Maybe it has. But, right or wrong, those people made the choice to engage in illegal behavior. They knew the risk.