My cousin was one of the reasons for the Cincinnati ban on pit bulls. When he was a kid back in the early 90's, he was seriously hurt, almost killed, by a pit bull that had been taught to be a "guard dog" by an idiot owner. Basically, they made the dog very people aggressive and when he broke free one day, he attacked my cousin and some other kids who were walking along a sidewalk. My cousin and his Mom have testified at some of the breed ban hearings. Of course, the dog breed takes the hit, not so much the idiot dog owners who mistrain and mistreat their dogs.
My thinking is that there are very few really bad/dangerous dogs but there are a significant number of otherwise good dogs who've been negatively shaped by bad life experiences and improper training, including lack of training. I don't think breed bans are effective since they don't do anything to address bad owners. Like you said, it's a quick political fix.