Tyranny of Civility
The “tyranny of civility” refers to the suppression of unwelcome or discomfort-generating opinions by accusing the people expressing those opinions of being “uncivil” or "out of bounds" in some way, either in the substance of those opinions or in the manner of expressing them. Once seen or labeled as “uncivil”, the unwelcome opinions and the people holding them, or the discomfort-generating situations and the people in them, can then be written off as unworthy of response or consideration.
Whether or not the unwelcome voices are, in fact, being “uncivil” is not the essential element here, but, rather, whether the accusation of incivility (whether accurate or not) is used to suppress or disengage from the substance, the content, of what those unwelcome voices are saying.
This strategy is often used by those in a position of power or privilege: a boss may coolly institute changes at the workplace that adversely affect the workers and then refuse to meaningfully engage with their protestations by objecting to any tinge of emotional charge that may accompany those protestations; facilitators of a public meeting may be able to suppress dissident voices if those voices can be labeled as “strident”; oppressed people fighting for their rights may be written off as “militant” (or even “terrorist”) by the media of the country oppressing them.
The tyranny of civility is often felt in board rooms, or in presidential debates, or in teachers conferences, or in police stations, where it is often the person speaking most eloquently or in the most even tones (and in an accent associated with a power elite) that is perceived to be the one with the best ideas, or is declared “the winner”, or stands the best chances of promotion; or it is the person that appears to be the least perturbable and outwardly most compliant and peaceful who is most likely to get a fair hearing of their grievance--whereas, in truth, the outward form of civility sometimes hides the very worst of motives and some very bad ideas, while the outward form of incivility (a raised voice, agitated gestures, impatience) sometimes indicates nothing but a very human response to stress or injustice...or the prophetic tone of someone speaking truth to power.
The tyranny of civility lends itself to use by those with structural power because people in positions of power generally do not have to shout to be heard. The marginalized and disenfranchised, in contrast, often have to take to the streets in large numbers, megaphone in hand, in order to be heard. However, the tyranny of civility may also be used by people who are not in a position of power, but who nevertheless wish to silence dissident or unwelcome voices and avoid engaging with them by labeling them (either accurately or inaccurately) as "unacceptable" in some way--as "bigoted" or "racist" or "homophobic" or "misogynist", for example.
Both the political right and the political left are sometimes guilty of using the tyranny of civility to disengage from discussion and to enforce anything from conservative codes of morality to liberal political correctness. The political center is perhaps the most egregious suppressor of dissident voices simply by virtue of posing as the reasonable middle compared with which all other viewpoints must by definition be "extreme" or "out of bounds" or "unacceptable" in some way.