Pitbull genetics have regressed horribly over the last 30 years due to the upswing in back yard breeders in the states. There are way too many dogs with shitty temperaments being bred.
Unfortunately, you guys can cry all you want that it's not the breed, it's the owner, but it's bullshit. Owner can help mask the genetic problems that these dogs have, but once they reach sexual maturity, they are loaded guns and should be treated as such.
And just so you don't think I'm some biased anti- Pit Bull fanatic, here is a picture of my 4 month old:
As long as Pitbulls remain popular and cheap, dogs with the wrong temperament will continue to pass their aggressive tendencies on. The breed needs a major clean up.