I've known three Pit Bulls in my life. I spent years of my life with them. I've been bitten three times, by a Chow, a Collie and a Shepherd.
Investigate the people raising the dogs wrong, or place some responsibility on people buying dogs bred from wrongly raised parent breeds. It's nurture, not nature.
Now, I'm not saying that aspects of their nature doesn't make them more dangerous than other breeds when the nurture makes them monsters. Such is the case, but I've seen some of the most vicious and snarling dogs be breeds most consider "family" and "friendly" breeds.
I recall that Pit Bulls were once used as rescue dogs.