Pit bulls have been bred to be aggressive. I know a guy who was riding in another friends car one time and a pit bull practically ripped his face off. Unprovoked and this guy had grown up with the dog. These are dangerous dogs, I don't think there is any questioning that. Some of them are nice. I like pit bulls but I think questioning there aggressive or protective genes is like denying global warming at this point.
Also pit bulls might not have the number one dog attacks per breed in a year, but I would wager they are the top breed % wise because of thier numbers. Practically 5% of black labs could be mean and there would still be more lab attacks than if half of the pit bulls in th country attacked someone.