Ive got personal opinions that would never stand up to your guys' wealth of pot knowledge but maybe a few can give reason.
-People who say pot smokers don't get violent are wrong, I've seen groups of guys high get destructive and smash tons of personal/public property.
-Pot smokers try to drive because they think they can, however they cannot, they have slower coordination and worse judgment. Anybody who says they drive better high, is the same to me as someone saying they drive better drunk, and no one is ever going to believe that
-Health reasons: Namely more tar then a cigarette, and testi cancer. Plus 2nd hand smoke could possibly get someone high that shouldn't or can't be.
-It IS a gateway drug, I've seen plenty of people go on to heroine or cocaine. And yes I've known people who were shot at/robbed for weed
- Laziness and a desire to not do shit becomes that much worse when people smoke it before school or before work, and too many people already do. It makes education a waste of money, either personal or taxpayer, and it can create a dangerous situation at work.
- That also leads to losing a job which means your family suffers, either your own wife and kids if you have any, or your parents that are now paying for everything
I will say this, I really don't care if people use it responsibly in their own homes, and I would vote to allow that in a perfect world. The problem is a lot of people don't do it safely/responsibly and it ends up affecting a lot of other people/friends/family.