My theory is anyone that can abuse an animal can abuse a person.
I do have to disagree a little with you though Audiosouce. There are some animals that are just not meant to be around people. I've had all breeds of dog in my home including 2 pitbulls I watched for a shelter for a month or two so that they wouldn't be put down. (to be honest pitbulls scare me and I do think they should be banned from cities, but these two were gentle and very well behaved, always glad to sleep on the couch next to me) I've only ever owned one dog that weighed less than 60 lbs, and it was the most hyper-aggressive and just plain vicious animal I've ever seen. It was this little 15-20lb wire fox terrier that I received as a birthday gift when I was around 7. We got him as a pup and brought him up right, but he was a bad dog. No amount of attention, no amount of treats, or petting, or training, or even punishement would change him. He killed my sister's puppy, nearly killed the neighbour's dog when it jumped our fence, killed our neighbour's rabbits in Germany, and attacked any person it though wouldn't fight back, especially me. It wasn't until I was ten and much bigger than the dog that it stopped biting me. When it bit one of my friends my parents got rid of the thing. To this day I hate wire fox terriers. I also know now that there are enough good animals in need of a home that you never need to waste your time on that one in a hundred just plain mean animal. My vet has a story about a guy trapped in his bathroom by his cat that is hillarious. This guy adopted a stray cat, and the day it moved in it started attacking him, and did so for months to come. He called the vet from the bathroom and asked her what to do. She said bring it in, put it down, and adopt a cat from the pound that would love to be with you.
I do think that some breeds are more predisposed to being violent. Terriers especially. That is why I'm a big boxer, mastiff, german sheppard fan. Big dogs with no terrier in them that were never bred (originally) to be fighting animals. For me a dog must weigh more than 40 lbs otherwise it is a cat that needs to be walked. I think for my next dog I'm going to get an Akita. I'm not sure though.