If we feel an urge to hit the enemy tribesman with a huge rock and take their land, we can and should say “No, there are >complex game theoretical reasons why this is a bad idea” and suppress the urge.

I may be misreading this, but I don't see it that way. There aren't complex reasons not to do that; there are relatively simple reasons not to kill people and take their stuff. The phrase sounds, to me, like, "Something bad may happen to me by engaging in this warlike behavior," but I think this is wrong both practically and normatively. Practically, whomping people has been successful for those with superior whomping power. Normatively, it's a utilitarian net loss to whomp people and take their stuff.

It's surely possible that I've misread this in some important way.