George,
This is simply not true. A hen's genetics are 50% the rooster that she was born from. When you put selective pressure on your roosters, you ARE putting selective pressure on your hens. If you're back breeding, and not swapping roosters every year, your hens are going to get most of their genetics from the rooster.
The offspring of a hen backbred to her father gets 75% of it's DNA from the father. If you don't think that puts selective pressure on the female line, you don't understand how selection works. As long as you're not replacing your rooster every generation, your population is going to drift toward the rooster.
Chickens are the opposite of humans - Males are ZZ and females are ZW - the only things you can't select via the males are genes specifically on the W chromosome. At this point there's absolutely no evidence that the genes that cause human aggression are on the sex specific chromosomes.