What I hate is the habit of avoiding a debate by condemning as evil and beyond the pale the person who expresses views contrary to yours. The discussion is never about the arguments and the evidence. It’s always, “You are such a horrible person that you shouldn’t express any opinions at all.”
Once you’ve got your opponent to try to argue weakly and pathetically, “No, I’m not evil! I’m actually a good person!” you have won the debate. And it doesn’t matter how weak your arguments were.