I don't really think you have been able to grasp or respect what a dog is capable of. Yes, you have more muscle in you arm then most dogs have in their arms but the fact is, though, a fighting dog is able to conserve and use more of its muscles in ways that no human can. I do believe a lot of people can get away from an aggressing dog, but not without harm and most likely not being able to kill it. A pit bull becomes very tense and rigid to the point that its muscles seriously feel rock hard. I doubt most people would be able to hold on to a dog like that. I also can't imagine anyone being able to choke one out or snap it's neck because it would be nearly impossible to turn a tense dog's neck.
I'm speaking hand-to-hand and as if the human does not have any weapon of any sort.