I have seen pit bulls that the owner tried to make mean (fucking asshole) in a tiny apartment, who were the sweetest dogs ever, and ones that were well treated with room to roam who were aggressive.

It's in their breeding, they're fighting dogs, bred to take down bulls. They tend to be really sweet towards adults, particularly men, ones that weren't got bred out. The problem is in other animals, children, and even women. Anything that tweaks their predator instinct. Some are worse than others.

They just have too much killing potential to trust to typical pet owners though.