Most people believe there are rules of civility that ought to govern our discourse in moral and political disagreements. These rules operate like the rules of just-war theory: easy to adhere to in theory, but in practice routinely abandoned by all parties for the sake of winning. Drawing on conflict theory and social psychology, I explain how social conflicts make it possible for people to break their own rules of engagement without recognizing that they are doing so. Indeed, the same public figures who speak of the need for civility and unity are often the ones most willing to resort to uncivil and intentionally divisive speech. In any “us versus them” conflict, the perceived necessity for “us” to prevail over “them” tends to outweigh other ethical considerations. The rules of civility, whatever their merits as an ethical theory, are largely ineffective at constraining immoral practices when the chips are down.