All dogs are carnivores, although they do eat some plant food. Dangerous dogs are bred for their tendency to attack. They have the heightened instinct to kill. Other dogs, such as golden retrievers, have a reduced instinct of attacking, but they have a heightened instinct to fetch and retrieve prey. Border collies, in contrast, have heightened instincts to stalk but they have no desire to retrieve or attack.
The wolf ancestor of the dog is a predator, and predators have instincts to stalk, attack and retrieve prey. All 3 types of behavior are needed for a predator to survive in the wild. If we put a border collie in the wild, it will starve to death because it will spend all day stalking animals without killing any. Same thing with attack dogs. They may keep killing but they may not know that they need to eat what they kill. A golden retriever may spend all day looking for things to retrieve but it may not stalk or kill prey.