If they turn around the vote and outlaw it based on harmful effects, then that could open up a can of worms/arguments on a lot of other things. OTC pain killers are harmful to the body, caffeine can kill, and that could even have people try to bring back prohibition and outlaw tobacco.
Personally, I say if people want to smoke it, they can't complain about possible side effects. If they don't want to take a chance on those side effects, don't touch the stuff, even if it becomes legal.