I can't speak for every dog and every dog owner, though many anti-pit bull people will tell you they can and that they're all just waiting to bite the face off a child.
What I can say is that, of the pit bulls and pit bull mixes I know, they're lovable softies with their owners, and I know one (our neighbors) that I can say with confidence could not/would not hurt anyone or anything else, as even when another dog attacked him he would not fight back. This dog is in a house with multiple small children, numerous cats, chickens, a turkey, and over multiple years being their neighbor I've never heard of him being hostile towards any of them, he's always been a Very Good Boy.
What I believe it comes down to is that pit bulls are big, strong dogs, with strong jaws, and some people are neglectful owners who fail to socialize them and train them properly. A poorly trained and poorly socialized Yorkie will bite you all the same, it's just you can punt one like a football. People who are not prepared to train their dogs to behave appropriately -- which is a part of caring for them, just as important as grooming or feeding them if not even more important -- should not own dogs, full stop, irrespective of breed.
It is, however, much easier for other people to blame the dog, have the dog put down (and let me say, if they did something bad enough to earn an early departure across the rainbow bridge, rightly so), and then promptly forget about the owner who didn't bother to train them. The owner who will, then, almost certainly, get another dog to neglect.
