x2 dogs are pack animal, will always submit to the alpha, and will always look to get a paw up in the pecking order.
Lot of folk put human emotions on dogs, its delusional, dogs are like woman, they must submit or fuck off.
Yup - a dog killing a kid is often nothing more than the dog asserting its position in the pack it perceives it is living in.
Probably wouldn't even kill another dog in a pack situation - or the other dog would bow down and give up that position before an attack took place.
Either way - you cannot train a dog to not be a dog. Not that most people train dogs anyway - they just treat them like babies, see them respond like babies a lot of the time & end up confused when they rip a kids face off.