i don't have dogs but i've always had cats and i'm an animal lover in general. i think all animals have wild instincts and if provoked in a certain way or to a certain degree they are going to react with their instinct. but we domesticate them and love them and so they become sweet and affectionate, and for the most part because they are living their lives with us in our homes, they are never really provoked to the point that their natural instincts take over. but make no mistake, my cat playfully bites me and it's sweet and i know he isn't trying to hurt me, but if i pushed him over the edge, his instinct would take over and he's attack. it wouldn't matter because i'm so much bigger and stronger than him, but if he was the size of a bobcat? a tiger? i'd be dead. EVEN THOUGH HE LOVES ME MORE THAN ANY HUMAN EVER HAS! it doesn't matter. instinct can never be erased, it's subconscious. so i think the deal with pitbulls is that they are built a certain way with certain DNA that makes them strong/capable enough to seriously injure (or even kill) a human, and if that instinct is provoked, there's no turning back. with other breeds, they may not have the same strength, size, or anatomy, so even if they did attack it wouldn't cause the same damage. there is no mammal that doesn't instinctively react when it feels physically threatened. even humans have instinctual defenses, which i learned early on in my martial arts training.