There are some virtues to this. Weeded out can mean less able to do worse things.
As usual, you are totally wrong. So black criminals get a license to sell mj legally. Then the money they make, the invest in heroin or crack, and sell that illegaly and make enough money to become bigtime drug dealers again. Plus plenty of people use mj and other drugs as well as booze, and commit all kinds of mayhem. A percentage of people who use mj go psycho, the rest become stupid and useless.