Many people enjoy discussing and judging the morals of characters in films, but that’s not the main point. Very few characters are entirely good or entirely evil, which tends to result in dull and poorly made movies. Regardless of whether viewers resonate with the story, they should show compassion for the characters. It’s important to interpret their motives and circumstances to understand what led them to make certain decisions and to reflect on ourselves.
I think that’s why he worked as such a good villain, because you understood his reasoning, which was terrifying. He was wrong, but you understood it, and you as the viewer knew that made him so much more dangerous.
If he just wanted to wipe out half of everyone that’d be boring and I wouldn’t feel invested.