The idea is that until and unless you actually carry through with what you say you're going to do (ie, wipe those dirty baby-eaters off the face of the earth), your people won't let you off the hook for that long enough to pay attention to your claims that those other guys are also baby-eaters.
Hatred isn't just a way to get some minor TO benefits against another realm. It actually means something in-game, and you have to take that into account.
