It's not the dog's fault, it's the owners fault completely. There's nothing wrong with pitbulls. They are just popular and thus tend to have douchebag owners. They're demonized by the media like dobermans and rotweilers before. Pitbulls are more headstrong so they need someone who is going to take the alpha role seriously. Otherwise they will gladly do it and they'll do the same to you that they do to other dogs in the pack who get out of line. Bites and growls. It doesn't mean they want to eat you, that's just how they communicate "you're out of line".
Your dad's friend or whoever is just a jackass, Green Man. He should have made sure the dog was trained to be controlled by others before he made someone else take care of it. She's confused, excited, stressed and full of energy. You'd be pissed too. But a good owner will train their dogs to deal with it properly before leaving it with someone or they'll pony up the cash to take it to a professional. My pitbull is sweeter than my damn poodle.
Also, any big (and young) dog requires a very disciplined walk. You can't just put it on a leash and try to take it for a walk. The walk is where you demonstrate who's in charge. Your dad's friend sounds like one of those douchebag owners if the dog won't even take a proper walk.
