Nick, based on your last post it's clear to me that it was just the dog's temperament. There was an unknown trigger there for aggression towards people. I'm guessing that that the dog was not reacting in an involuntary way, it was more of a conscious action. By this I simply mean that with strong enough negative consequences in every situation that made him fire (practically impossible to do) those dogs would have thought twice about it. I'm also guessing that it was based in dominance or social aggression as was previously discussed in another thread. As was also mentioned social aggression is probably not a good thing to bring into the bull breeds, as they don't appear to go through all the posturing that would give some warning and time to dissipate the situation. Rather they go full throttle every time they're stimulated, a very dangerous animal to keep around.