I believe there is an aggressive fighting gene bred into some dogs AND it's poor control of some pet-owner. There are parents who can make a genetically unsound children worse and potentially great kids bad. No one tests or holds some parents completely responsible for some behaviors but understood some things you have no control over but some you do. When he was six some other parent made a comment about my kid " He says thank you!! Where is he from, Mars?" Her kid was not welcomed at my house.