This point is in fact conceded by those who practice such things as colour discrimination. Few can be found who will explain their practice merely by saying, 'But they're black: and it is my moral principle to treat black men differently from others'. If any reasons are given at all, they will be reasons that seek to correlate the fact of blackness with certain other considerations which are at least candidates for relevance to the question of how a man should be treated: such as insensitivity, brute stupidity, ineducable irresponsibility, etc. Now these reasons are very often rationalizations, and the correlations claimed are either not really believed, or quite irrationally believed, by those who claim them. But this is a different point; the argument concerns what counts as a moral reason, and the rationalizer broadly agrees with others about what counts as such -- the trouble with him is that his reasons are dictated by his politics, and not conversely. The Nazis' 'anthropologists' who tried to construct theories of Aryanism were paying, in very poor coin, the homage of irrationality to reason.Bernard Williams, "The Idea of Equality," in P. Laslett & W.G. Runciman (eds.), Philosophy, Politics, and Society (Oxford: Blackwell 1962), 112-17.
That last line, about paying "the homage of irrationality to reason", is what earns the quote a place on the blog. But the whole argument matters. Again, virtually all assertions of hate against a particular outgroup are dressed up in this sort of garb -- albeit some wearing more layers than others. Recall the "bombing a synagogue isn't antisemitic if its based on dislike for Israel" case. They don't hate Jews, the argument goes, they hate alleged bad conduct done by Jews. But this is utterly ordinary as a case of antisemitism. People who hate Jews do so, they say, because Jews are greedy, or bloodthirsty, or conniving, or murderers. It virtually never unadorned, and so the fact of adornment itself doesn't falsify the hypothesis that the attitude is discriminatory.