Calvina, did you not study in history class?

Calvina Fay, executive director of Drug Free America Foundation, strong disagrees. “I can’t understand how anyone thinks that legalizing drugs is going to stop the violence," she said. "To think that drug traffickers in Mexico are going to fall in line and pay their taxes if marijuana is legalized is just flawed thinking.” see the complete story here
Now not to beat a dead horse with a stick, I will point out this. Back in the 30's when alcohol was illegal on the federal level there was violence and crime bred into the industry. Which was a problem quickly eradicated by legalizing alcohol.