At the risk of being late to the aquarium, I'll say this: yes, the insistence on civility *is* a silencing tactic. Among others- accept without question what a white, or male person says, but expect people of color and women to have higher standards of evidence, don't allow people of color or women to react against obvious lies, like 'women who have abortion are sluts who hate babies' or black people steal white people's 'spots'- expect a small careful civil debunking of every single little lie, no matter how obvious, let anti feminist men and women have the last word on sexism or white people define what racism is- even if they haven't studied race one bit! Excuse racism as the problem of a 'minority' contrary to fact, or sexism as the problem of those savages over there. Due to these tactics, white liberals/ liberal men(and woman hating women) can think they are good people, while also having fun by helping oppression along.