Dogs are loyal/obedient. They do what they are trained to do. If that means attacking intruders, they will do so, not knowing any better.
If you love a dog, and teach it to love and respond to love, they will never be aggressive. “Raise your kids like puppies and your puppies like kids, and you’ll never have any trouble with either.”
(Ah has SPOKE!) [Mammy Yokum]