Let me make this even clearer to you: breed genetics are a large part of behaviour.
I didn't have a rat problem.
I didn't teach my dog to go ratting.
He comes from a long line of dogs bred to hunt rats, and he hunts small furry things because it's hardwired.
XL Bully owners might just buy one because they like them. That doesn't mean that the dog isn't going to intimidate people, guard their owners and property, and fight in the right circumstances.
Training and socialisation can only do so much; breed genetics are also very important. No matter how much training I put in, mine is never going to herd sheep, for instance, and nor is an XL Bully. Border Collies on the other hand? They'll make their first attempts at herding when very young, on sheer instinct.