I'm not a professional anthropologist, but I have never come across a society which does not view that which preys upon it as monstrous.

Let's say demons — at least in the Christian tradition, this is the case, although they've hardly patented the concept — are categorically incapable of kindness. Actual kindness, not out of a desire to manipulate a given victim. Can meta-ethical moral relativism apply to something which is supernaturally compelled to victimize another population?

I don't disagree with you, for the record, but I don't have a personal horse in this particular race. [ well. not in the sense that she's keen to create her own hard and fast definition of 'monster.' ]