I've got a pitbull that's the same way. Clipped me a good one on my mouth when we first got him at six weeks old. My hands looked like baby sharks just got done biting at my hands for months, but I just count that down to it just being his nature. Give him a reason and he'll show you how he feels. He just needed to learn how to act, not that he never could learn. Now he knows not to put his teeth on anyone, though he'll give me a slight touch as in to tell me to get off when I rub him too much.
But bring him around anyone that isn't me? He'll lick you to death and give you enough love for two life times. He's only off the leash when I know I won't have to chase him down and keep him from throwing himself on someone.
