Bullies actually weren’t. They were bred to be strong, but another goal was to for the breed to have a lowered prey drive.
The reason why they’re so dangerous is because if one does become aggressive, then it is more than capable of completely ripping you apart. There are, however, breeds of dogs designed to defend livestock and homes (attacking intruders like animals or humans), but most of those are very rarely banned because they’re typically trained by a professional instead of a random chav who wants a dog to boost his ego because he can’t own a gun. Some examples are: Komondors, Great Pyrenees, Tibetan Mastiffs, Rottweilers, German Shepherds, Doberman Pinschers, and yes, Pitbulls (but not bullies).
Any dog can be trained to be aggressive (except maybe golden retrievers). Any dog can be mishandled, abused, beaten, or otherwise conditioned to lash out at someone. Stop blaming the dog and instead blame the human. The dog does what it’s been trained to do and if it’s been improperly trained, then it will appear to act erratically and lash out at random people, regardless of whether they’re a threat.