Robert B. Talisse in at ARC Digital:
We tend to think of civility as maintaining a courteous and calm demeanor in political debate. But that can’t be correct. Keeping your cool is good, but courtesy and calmness can also be patronizing. Moreover, fervor is sometimes called for in politics. So civility is better understood as the avoidance of gratuitous escalation and excessive hostility. This allows for political antagonism but recognizes its limits.
Civility, then, is a matter of our internal temperament rather than observable features of our behavior. In judging someone to be uncivil, we do not point simply to their aggravated manner. Instead, we assess the appropriateness of their behavior; we evaluate their motives.
This makes civility more difficult than it seems. In order to regard others as civil, we must ascribe to them the disposition to engage in good faith. However, when it comes to our political opponents, we systematically ascribe negative traits and motives such as closed-mindedness, untrustworthiness, and dishonesty. Behavior that we condemn when performed by political opponents nonetheless strikes us as excusable, or even admirable, when enacted by our allies. When forced to admit our side’s wrongdoing, we promptly forgive; we regard similar infractions from other side as unpardonable.
More here.