While individual dogs may not adhere to breed traits- I would say that on average dogs of certain breeds do possess certain shared traits that are common to their breed. That's the whole point of creating breeds you want to have dogs that for the most part look and act (or have a similar temperament) like one another. "Pit bulls" as a breed are characterized by aggression and also a strong "fighting spirit". Think about it the breed was originally created for bull baiting and then used for dog fighting and to a lesser extent hunting/ranching. There is a reason why this breed, even into the present day, is so commonly used in dog fighting. I remember also reading somewhere that drug dealers were the first to cross-breed them en masse with shepherd dogs to try and create the "ultimate" guard dog for their stash house for instance. You get the human diected aggression and guarding qualities of a guard/shepherd dog with the general aggression and fighting nature/strong don't back down spirit of a pitbull. This is why you see or hear stories of huge 100 plus pound pitbulls (they are often mixed with other breeds) who maim their owners or another person.
Now I think one of the problems is that there only seem to be two extremes BSL or basically a free for all ownership. Banning felons from owning this dog which has been done in some cases is only part of the problem. While having people who abuse dogs of this breed and deliberately make them as aggressive as possible certainly hasn't helped this breed you also have well meaning owners who want this breed or other large dog breeds but they don't bother or have no idea how to properly train them. I think it is problematic and I am definitely not in favor that anyone off the street can buy a large, powerful and potentially aggressive dog breed and yet have zero knowledge of properly training it, but a BSL may not be the answer either. IMO but I don't think these breeds are for everyone...