I had a gorgeous female pit, who started out to be the most loving animal. She would lick you death. I never thought that she would ever attempt to hurt anyone, but she did. She went after my son ( I thought he was telling stories, so I went to check on her and she just wanted to lick all over me), so I sent my husband out to check on her, and she went after him, then she went after my brother-n-law. I do not know what changed her, but she had to be put down. I don't think there all bad, and I don't think that they will all turn, but mine was basically a rescue. She came up starving to death, so maybe a man abused her, because she was only doing this to men and not women.
I also had a 1/2 pit 1/2 chow for 14 years, and he was the best dog anyone could ever hope for.
But, I'm really glad that they were able to rehome some of the pits and that they will no longer be abused. I think it's all in the way that they raised. You can raise them to be mean or you can raise them with love and they will love back.