I've never owned a pit, but several of my friends have in the past. The only time I've seen these animals get aggressive, they thought I shouldn't be there or were taken by surprise. A simple scolding by the owner and the dog laid down and went back to a lump on the carpet or changed demeanor and asked for a little loving. I've seen the same traits in the labs/ shepherds I had growing up. Dogs are meant to be big (good first line of home defense). I don't discriminate against breeds but am always cautious around an unfamiliar animal- regardless of size.