You're Not Just Trying To Start A Debate
|As we often have to point out, while politeness is a virtue, it is of minuscule importance when compared with robust debate and discussion.|
The problem with this argument is not that it's wrong (though calling political correctness "politeness" tends to trivialize the real motivations behind it), but that it's so rarely actually applicable. Incidents of "PC censorship" are very rarely provoked by someone trying to honestly engage in "robust debate and discussion" about their unorthodox view, though the provocateur and his defenders immediately claim that motivation. The forum and the phrasing are almost never what one would choose if one wanted to start a genuine debate aimed at open-minded exploration of ideas.
The "I was just trying to start a debate" defense concedes too much, because speech need not be aimed at open-minded debate in order to be defensible. Speech is valuable as expressive conduct -- it allows you to make your views known, and make them known in the terms that you hold them, rather than terms chosen carefully to appeal to others' framings. Expressive speech lays a claim to recognition, as an agent who can frame his or her own viewpoint. I would note that far-left protests against center-left demands for "civility" tend to get this point right -- the right to be uncivil is typically grounded in the need to authentically express oneself, not in claims that they are just trying to engage in "robust debate."