Most of us recognized this problem long ago (who else remembers the “tone wars” on ScienceBlogs?), but it’s good to have a good summary of the problem with emphasizing politeness.
When used as a political rallying point, appeals to civility are often a trap, particularly when forwarded in response to critical, dissenting speech. Sidestepping the content of a critique in order to police the tone of that critique—a strategy employed with particular vigor during the Kavanaugh hearings, and which frequently factors into hand-wringing over anti-racist activism—serves to falsey equate civility with politeness, and politeness with the democratic ideal. In short: you are being civil when you don’t ruffle my feathers, which is to say, when I don’t have to hear your grievance.
Besides their tendency to be adopted as bad faith, rhetorical sleights-of-hand, calls for civility have another, perhaps more insidious, consequence: deflecting blame. It’s everybody else’s behavior, they’re the ones who need to start acting right. They’re the ones who need to control themselves. In these instances, “We need to restore civility” becomes an exercise in finger pointing. You’re the one who isn’t being civil. Indeed, the above NPR survey explicitly asked respondents to identify who was to blame for the lack of civility in Washington, with four possible choices: President Trump, Republicans in Congress, Democrats in Congress, or the media. Whose fault is it: this is how the civility question tends to be framed.
Just remember, Nazis can be civil. It’s not how they say it that matters, but what they say.