Says you. I guess you haven't known someone injured by a driver on this.
What legal ramifications were imposed on the driver?
No. But I logged many tens of thousands of trouble free miles back in a more foolish time. It causes absent mindedness and inatentiveness that obviously isn't a good thing. But it just doesn't cause the motor skill impairment that makes alcohol so deadly. I'd estimate that, compared to cell phone users, your average stoned driver with two hands on the wheel is one tenth the risk.
The thing about not knowing anybody injured is demonstrative of nothing. I know numerous people killed and injured by perfectly sober drivers. Should we go after sober driving? Any accident has a few contributing factors. Marijuana use on its own is rarely at the top of the list. I'm not saying it should be legal to drive stoned. It is certainly a hazard to some degree. But there are far bigger hazards on the road.