Purebred dogs all exist for a reason. Rottweilers were butcher's dogs used to pull carts, and drive cattle. Dauschhunds were used to hunt burrowing animals, especially badgers. Newfoundlands to retreive fishermen's nets from deep and cold water.
Pitbulls? To fight.
This doesn't make the 'bad dogs' to me. Terriers have a heightened prey drive; we bred them to so they'd be good ratters. Pitbulls were selectively bred for a hightened prey drive coupled with intense tenacity and strength. HUMANS made them that way. When they fight, they're doing what they were designed to do.
I don't condone dogfighting- I think bloodsports of any type are barbaric and inhumane. But in the recent past every country in the world had their own versions. Pitbulls are a remainder of this culture in America.