Pitt Bulls were bred to be aggressive and to attack. It is a manipulated type of dog. Wolves can be bred to be domesticated submissive dogs in just 8 generations. The opposite is also true.
The problem with pit bulls/pit bull mixes is that you never know. They can be lovable, wonderful and loyal dogs for years, then suddenly turn. Not all, but enough to be very wary of them. You just never know. Not worth the risk for us to have one.