It’s the owners that teach them to be vicious.
Not necessarily. We had 2 pitbull mix. One male, one female, both rescue puppies They were wonderful until one day a cat got into the fenced backyard. I was in the kitchen when I heard the commotion. They killed the cat and ripped it to pieces. I was devastated. I put the dogs in the kitchen and closed the screen door. I bent over to pick up the cat and Daisy came through the screen and attacked me. Grabbing my arm and shook me like a rag doll. Duke wasn’t far behind and tried to get my other arm. I just happened to get free and back into the house. Several stitches later and a couple of surgeries. We never beat the dogs, or hit them at any time. They were great with the grandchildren. I don’t exactly know what turned on in their brain but they never stopped as I was screaming at them.
It’s a primal urge. Needless to say we had them euthanized. I could never trust them again.
Both of my kids were seriously bitten by dogs, a black lab and a German shepherd (separate incidents).
Both almost lost an eye. My son also lost a tooth, my daughter had a puncture wound inside her mouth.
Both had many stitches. I have pictures.
I would never, ever own a dog. Both of my kids now have families of their own and each has a dog.