There is no such thing as a bad dog, only bad owners. And that goes for all breeds, from a chihuahua to a doberman. A dog that is trained to attack other dogs or people that the owner sics it on, does not know its doing something wrong. It has been rewarded by the owner to do that stuff, so it just trying to please the owner. And people think that these breeds will turn on their owners, and that is a possibility, only if the owner hasn't trained or socialized the dog. These "dangerous,visious" breeds do just as well in a family as any other "gentler" breed. People are just biased towards them, from what they've heard.