I breed game chickens and when an human-aggressive male is encountered and the aggressive nature is suspected of being genetic, the bird is promptly culled. Such selection has resulted in games being among the most docile breeds for handling. Sometimes the aggressiveness stems botched handling which is hard to correct for but that will be a reason to not employ harsh culling. I am using the same logic with my dominiques since goal is to have a dual purpose breed that can forage when and where kids play without causing me undo worry.I was told by several breeders that aggressive cocks produce aggressive male offspring. I won't breed a highly aggressive cock.