Evil absolutely exists. Pretending it doesn’t is a device of people who have some vested interest in ignoring it, or people who are so limited by their own comfortable experience that they have never been confronted by it.
I have been reading Team of Rivals, a deep dive book about Lincoln’s presidential cabinet during the civil war. It is amazing that many of the men write about how, after having personally witnessed slavery, they then vigorously oppose it. (Seward, for example, goes on a trip to the South for vacation and basically comes back hating slavery because it is so clearly wicked).
I imagine human sacrifice, death camps, gulags, they all evoke similar responses. ‘Societal good can only be reached through mass slaughter of the undesirable’ is the subtext. That should be repulsive to any with a functional moral core. The amount of suffering enacted by the Aztecs as they killed their neighbors children… I can’t imagine.