Dogs are pack animals. When they feel threatened, they will defend themselves. They will also protect other members of the pack to a certain extent. How they defend themselves, and how close they feel to the rest of the pack (their owners) depends on the dog's nature. It also depends on how they were raised. Since dogs judge dangerous situations differently, they should not be left unattended near a place where people are arguing. They may also judge "unattended" moves of a child as an attack. Therefore, dogs should not be left alone near children.