By Cesar Millan Dog aggression is a major dog problem for owners. I want to help you understand the causes of dog aggression, so you can overcome this dog problem. Dog aggression stems from the dog's frustration and dominance. The dog's frustration comes from a lack of dog exercise, and the dog's dominance comes from a lack of calm-assertive leadership. Breed and dog aggression I deal with a lot of red zone dog behavior cases, and I often hear people incorrectly blaming the breed. Any breed can cause trouble. The difference between an aggressive Chihuahua and an aggressive pit bull is that the bigger breeds can cause proportionately bigger damage.