I was riding my bike in rural Minnesota, when a large collie ran up; jumped against my bike, then bit my thigh. A triangular pattern of tooth marks punctured the skin through my jeans. After that one bite, he ran away. His owner came and apologized. She assured me that her dog's immunizations were current. She also explained that her dog was repeatedly tormented by boys on bikes throwing rocks at him.
He was confined briefly at the Vet's. My physician billed the dog's owner for the only medical care I needed -- a tetanus shot.
Here was a collie with a history of abuse, yet I was not severely injured, nor my life threatened. This convinced me that how a dog is treated doesn't necessarily determine how they behave, or this dog might have killed me. More important is which traits are emphasized in developing a breed. Collies were bred to herd sheep. This explains why an abused collie wasn't as dangerous as certain other dogs; and why sexually mature pit bulls are the breed most often in the news.