I thought it was about not thinking deeply enough, like what ramifications your actions will have to the people around you in the long term.
Like, "I probably shouldn't rape this villager because she might be traumatized."
Oh, sure, the shallow villain might rape and pillage because the impulse grabs them.
Then when you think, "What am I doing, she's getting hurt by this?"
But you can go even deeper. Think, "What do I care if she's traumatized? I owe nothing to this person. She's of no use to me, and there's no reward for *not* raping her...so I might as well do it if it makes me feel good".
Of course, that's still rather careless and short-sighted. But in the end, evil is about complete despair and realizing that there's no point to anything, and trying to share that viewpoint with others in any way you can, for it's own sake.
It takes a lot of deep contemplation to sink that far.