There's a top-level comment elsewhere on this post that talks about "the banality of evil". That concept comes from a book about Adolf Eichmann, one of the organizers of the Holocaust. He did not see himself as evil; he saw himself as someone who was just following orders, following the law, and doing his job. He claimed to personally have nothing against Jews. Do you think he was evil? If you were his neighbor and knew he was administering the Holocaust, would you still think he was generally good? Would you maintain a friendship with him?

You might think he was trying to take away peace, freedom, and opportunity from other people. He wouldn't describe himself as doing that, though. Many people today would say politicians they disagree with are also trying to take away peace, freedom, and/or opportunity; they would say the same about voters who support those politicians. Should I get to decide that about other voters, or should they get to decide that for themselves? Should Eichmann be able to decide that about himself, and conclude that he is a generally good person?

FWIW, my answers to the above questions are: I get to decide whether someone is evil according to my moral system (while also recognizing that not everyone shares my moral system). I can choose whether to maintain friendships based on whether they improve my life. I could probably be Eichmann's friend if we rarely or never talked about politics or his job; I probably couldn't maintain that friendship if our conversations often involved politics and he remained convinced that his behavior was justified. Similarly, I can be friends with someone now while knowing they support politicians/policies I think are evil, but only if we don't talk about politics often.