The concept of a "fighting bloodline" in dogs is controversial and not supported by scientific evidence. Dogs are individuals, and their behavior is influenced by a variety of factors, including genetics, environment, training, and socialization. While certain breeds may have been historically associated with certain traits or behaviors, these traits are not innate and can vary greatly within the breed.
Additionally, the term "fighting bloodline" is often used in a derogatory manner and perpetuates negative stereotypes about certain breeds of dogs. It is important to remember that all dogs, regardless of their breed or background, have the potential to be loving and well-behaved companions when given proper care, training, and socialization.