I have exactly one friend who has had a dog that was attacked by another dog. The dog doing the attacking was a pitbull.
I also have exactly one friend whose dog attacked another dog. The dog doing the attacking was a pitbull. That pitbull was very loved and had no history of violence. Brought it into a vet and without provocation it latched onto another dog's neck. Thankfully they were already in a vet, otherwise the other dog probably would have died.
Very small sample size, of course. However, I do not know one single person who has a pitbull that doesn't think he/she is a total badass. They're buying an image with that dog. They want others to think they, personally, are a hardass. Without fail.