Honestly weed effects everyone different in regards to driving. To say it's not dangerous outright, is the same thing as saying it is dangerous outright... neither are true.
Most the weed I've smoked, I wouldn't dare go near a car because it fucks me up so much, that I know operating an automobile myself is not safe for anyone. In fact, the second or third time I smoked weed, I was in my car and had to drive home. I was messed up enough to blow right through a red light, which I consider pretty dangerous. Who's to say it was because of the weed, but I had never blown a red light before that.
Alcohol on the other hand, anything under 10 shots doesn't impair me enough to ensure I run over curbs, speed, or fail to maintain lanes. I don't have experience with this, but alcohol just doesn't screw me up the way weed does. I feel like I'm more under control with alcohol.
And there have been accidents causes by driving while stoned/high. I can try to link you to some reports, if you really wish to believe that it can't be dangerous. Everyone is different.