When pit bulls are violent toward people, it generally indicates a problem, perhaps lack of socialization with humans, trauma, neglect or issues with training. (dogcare.dailypuppy.com)
If you are taking an older puppy, make sure it has had the necessary early socialization with humans and exposure to environments other than the kennel. (gatewaymsc.com)
However, they need plenty of opportunities for socialization with their human. (nehumanesociety.org)