Well, the pitbull is one of the only breeds that was purely bred to fight. Rottweilers were used as herding dogs as well as bull baiting, hounds were bred to hunt -with the taller ones being 'sight hounds' and the shorter ones being 'scent hounds', retrievers were bred to retrieve shit, Pointers were bred to point at shit, Ridgebacks were bred to hunt lions but the Pitbull was bred to fight. The issue also is with the Pitbull bite that it has a type of lock jaw mechanism and when it bites, often the aw has to be broken with a crowbar to release the grip.
I love the breed but there really should be licenses issued and training courses if one is going to ever own one. They are great dogs, one of the most loyal, affectionate and loving breeds, but in incompetent hands, they can be lethal.