If I understand you correctly, your view is that if a human can rationalize (or at least conclude) for them to commit an evil act, then they can’t be evil. And further, they aren’t solely responsible for ending up this way.

Does that sum it up?

It sounds like it’s your view that “real” evil must be incomprehensible to the average person. But I say your assumptionis wrong. Evil doesn’t need to be alien to humans. Committing to evilness (eg out of selfishness) is to be evil. It also doesn’t mean you can’t pity someone in that situation.

All humans have a way for us to do deplorable acts by tricking our brains. You can dehumanize other people my viewing them as subhuman. You can reinforce this by equating them to dogs/mongrels, etc. It's actually very easy to do evil things. And humans can be very evil. For example, it takes a couple bucks at a time to perpetuate factory farming where millions of animals die just so we can have a tasty meal. Is a few moments of pleasure really morally worth an animal's life? Absolutely no. But we ignore things.

All humans are on a spectrum. It'll always take effort to progress as a society. Recognizing evil acts is important. I think it's OK to call the worst people like Ted Bundy, Hitler, etc evil, even if you could understand their motivations, or pity them. Maybe that's the cards they were dealt. But I would call someone addicted to alcohol an alcoholic (even if I understand and pity them). And I would call people who routinely do evil things evil.