Hmm .. maybe you're right in that it's a matter of degrees. To me, there's a minimum amount of empathy that people should have, and below that I think they're crazy.

Psychology is not really a hard science, there is no real minimum or maximum requirements needed for a diagnosis. It's all subjective to how a patient interacts and behaves compared to the social normative.

To me, it still takes a crazy mind to look at a breathing mammal and straight up murder it.

Eh, I guess it just depends on your ethical construct. I'm mostly a vegetarian because of environmental reasons, that and I think that industrialized farming is morally abhorrent. I would much rather hunt, kill, and consume a deer than go to a Wendy's. There's a lot less suffering involved in virtually all hunting than just about any industrialized farm.