I have a hard time seeing why an animal with these characteristics is necessary. I have some neighbors who're on their second Doberman that's been very well trained to walk around the perimeter of their property and warn unwanted visitors away without menacing mere passers by. Most large, generally friendly dogs like Labs are still very protective of their families and will attack people who genuinely menace family members. Hence, I don't see any good reason to own an animal that's a four footed law suit waiting to happen.
Good question. Why would someone own a breed developed to fight and kill? Any redeeming features the breed has are merely accidental.
Another Law Enforcement Pit Bull termination operation here:
http://www.freerepublic.com/focus/f-chat/1627231/posts