As far as being intact versus spayed/neutered and biting goes, it boils down to hormones, and hormones have a huge role in a dog's temperament and actions. Not to say that all intact dogs will react violently in the same situations, but it's just more likely. This goes for -any- dog and -any- animal, not just pits.

You don't have to convince me that responsible owners can have pets that aren't spayed and neutered, as I said I used to be one of those, and my dog never got into a fight, was never aggressive, only got loose while in heat once (when I wasn't home and a family member was keeping an eye on her), and she never got pregnant. So I know it is entirely possible. I don't judge responsible or irresponsible owners solely on whether or not their dogs are fixed, in fact I try not to judge at all.

Oh, also another side note, I know in similar situations dogs can react one way or the other whether they are altered or not, it just so happens that statistically altered male pit bulls have never been the cause of a single human death in the history of dog attacks/bites in either the US or Missouri (I believe in the US though), and altered dogs - especially males - aren't driven by hormones as much as an intact dog would. I do not have the source of that information since it was given at a presentation from a guest speaker, however I can try to obtain it if you'd like since I found it -very- interesting.

I will say though, every pitty I've met in person, altered or not, has been a huge love-bug!