In my experience human aggression is very much genetic.
I have lots of "roosters". I usually have one hen per cock bird. Many times I drop a hen in a pen and let her get bred and then pick her up and take her back to her pen. My cock birds are like big friendly kittens. I can handle them and let children handle them, I can take them to agro-tourism events and they will set on my lap while busloads of screaming children descend upon them, and they don't try to fly away. Even without prior handling. Human aggressive birds are all but unheard of in the breeds that I work with. At the same time, they are extremely intra-male aggressive, as they are game chickens. Due to their heritage, they have been raised for many, many generations culled for showing signs of human aggression, to allow for the handling and conditioning, and daily care and interaction that went into these birds. Many of these tasks were carried out by small children, in some cultures. Therefore, these birds have a very laid back attitude toward their human handlers, even if those handlers are small children.
Contrasted to the meat, egg, and fluffy feather breeds, the production/exhibition breeds might have very little human interaction. A rooster in a breeding pen with plenty of hens and little handling may never show signs of human aggression that are carried and passed genetically. Some might be bred to and culled before ever reaching a mature enough state to become "mean". Still others will have this behavior excused if production or exhibition goals are met. So if you are working with the more standard breeds, you are faced with a genetic crap shoot, no matter what you do, but you can certainly bring things to a head quicker by certain actions.
