It seems like a lot of people assume that game breeds are the root of aggression, since they are bred for aggression. Nothing farther from the truth. Most of the old timers that raised games agreed that a rooster that attacked people was usually a coward. This trait was usually culled for immediately. Most rooster attacks are out of fear, or mental deficiencies in the rooster. The game breeds make some of the friendliest, non-aggressive pets that you could imagine, and can be very "gentlemanly" around hens. Modern production breeds are usually selected for color and conformation more than anything, and roosters are chosen long before they would be old enough to turn bad, all their brothers have long been in the freezer, so they are stuck as the main breeder. In contrast, the old game breeders had many males to choose from and usually didn't pick one to breed until it was two or three. Many of the oriental game breeders would spend considerable time with their roosters, bathing, hand feeding and exercising. Any bird with man fighting tendencies would most likely out himself under this scenario. Some production chickens could be horrible man fighters passing their genes freely, and because of how they are kept, no one will ever know. If they are not handled, have a bunch of hens, get some food poured in the feeder and not much human contact, as in breeding pens at a hatchery, most of the bad ones would never show themselves. Especially if they are rotated out before they hit two years old.
If someone wanted to raise chickens that didn't regularly turn out human aggressive roosters, there is a lot to be learned from some of the historical aspects of chicken keeping. This includes a hen selection. No point going through exhaustive vetting practices on your roosters if you are going to put them in a pen full of hens that half of them might be siring human aggressive roosters.
