No dog breed, historically, has been bred to kill and maim humans. Bull breeds were not bred to kill people. They were bred for bull baiting and specifically bred not to show any aggression towards their human handlers, even in states of high arousal, making them one of the "safest" breeds to keep around people, traditionally.
If this has changed, and I am not denying that these dogs have been the victim of decades of piss poor breeding, it is down to modern breeding practices and there is nothing stopping the people who have done this to bull breeds from moving on to labs, poodles, sighthounds, etc and doing the same to them.
The only way to stop this is to put tighter controls on breeding.
Plus, this "breed" is not a breed. It is a mixture of breeds, a mongrel, essentially, so the legislation to ban them will yet again be a set of nonsensical measurements that can just easily target completely innocent breeds.