That dog was also probably abused by some horrible owners. I've seen dogs that don't need any provacation to rip someone's face off. They've been through so much that they just snap for no reason. They're just like some people actually. If genetics had gotten THAT bad, Its a wonder how the dog was even bred without ripping apart it's mate.
Also I never said that genetics don't play a role in the lady getting mangled. I'm saying that that dog snapped and I've never heard of a dog, even with the worst genes, snap like that. Especially if it's had a proper upbringing. What makes it worse is that it was HER dog. It's not like it was a random dog walking down the street, it belonged to HER.
My friend rescued a pitbull that comes from what i would consider to be one of the worst gene pools. It's even been fought when younger, his dog get's along great with mine. It's possible that the dog snapped from just having bad genes but I think it's really unlikely.