Empathy erosion is a logical response. You know it is. Or you wouldn't be able to eat meat. If you turn the dial up all the way on empathy, you end up like that strange offshoot of Hinduism, walking around with your mouth covered for fear a fly will fly in and you'll swallow it. You'll do silly things like only eat fruit after it's fallen on it's own to the ground cuz you don't want to hurt the tree.
Come on. Really? Empathy erosion is a highly adaptive response that allows your survival. It allows you to kill the enemy and consequently survive. It lets you bonk the cow on the head and eat it as hamburgers. It lets you wring a chicken's neck and have fried chicken. It lets you grab that okra at the right time and cut it and bread it and fry it. (I'm having serious issues right now about wanting fatty stuff, have you noticed?)
So it would be a huge mistake for our very survival to do away with empathy erosion when we have a committed, dedicated enemy intent on our destruction. Except we don't always, or even often, have that, do we? And certainly, Baron-Cohen would argue that if we didn't suffer empathy erosion in the first place, we wouldn't have enemies.
Ah, well. When you face repeated insults, empathy erosion is a natural, self-protective feature. That might be a good thing to remember if you're trying to reach someone and win them over, that if you insult them, that ain't gonna happen. They'll be in the middle of having some serious empathy erosion for you. Now, if you have no intention of winning those folks over because you've already decided you don't want them on your team even if they came halfway to their senses, hammer away. Why not? It feels good to set that us-them divide up. We loved Red Rover, didn't we, as kids? All our games are set up as us-them. We hate the rival teams. Our culture is predicated on empathy erosion.
Seems to me that you're danged if you do, danged if you don't. And empathy erosion is an inevitable consequence of being human.
*Yeah, I'm a frakking ray of sunshine today.