Yes, it can be true. Some breeds, depending on their original vocation, were intended to possess a degree of dog aggressiveness. Examples would include fighting breeds, guard dog breeds, flock guardian breeds, some coaching breeds. This tendency served a purpose based on the sort of work for which the breeds we're created in the first place, so the genetic basis for it is there. In modern times, it has in many cases been at least partially eliminated, as DA is considered a cardinal sin by many people and one that rarely serves a purpose today since most dogs aren't used for their intended purpose any longer. But the genes are often still there.