I disagree with that usually a male only attacks a female, if the female is the leader of a pack, or over a dog bone, whatever !This is clearly not the case ! Black Labs are also supposed to be gentle and not aggressive.
So clearly in my opion there is something wrong with this picture. I've also had a black lab that lived for seventeen years and she was not aggressive
towards any other dog. None of the labs I've been around were aggressive like this either. With the average life span of a black lab being around nine years I might know a little bit about them. Yes, I still believe this to be a phsychological problem of some sort.