Briefly I thought of a crowd of rats beating zombies around as if they were worthless. Since they can't squeak the way a rat does, they just moan "braaaains" all day and mess the community up.

But zombies are badass and don't care in the slightest if they're beaten around. It doesn't help anyone heal. It's badass to not care if you're hurt, it's a cool trait that's held.