The more politically powerful a group is (like Whites), the more they will tend to scramble to appear "civilized" in front people with less power, to compensate for their racist/classist impulses and actions. That's my theory. The compulsion some have to appear excessively civilized or well-mannered, is also a subconscious means of downplaying all the stolen power they enjoy; all their unfairly attained White privilege. It's in the best interest of a such a person to downplay their racism and pretend their racism – and all racism – doesn't exist, to act like they couldn't possibly dislike you or your "kind"; to try and hold on to the benefits of all that racism by pretending to kill people with kindness. The term I use for this historical ritual is White Civility Disorder.
The British (among others) came to the US and called the Indians and Africans they raped, brutalized, killed and enslaved "savages", while greeting their fellow Whites "properly", creating elaborate "pomp and circumstance"-like rituals for each other, to be rolled out in open social interactions. It was a form of denial; a way to say, “We are good, righteous people. Just look how nice we are to each other.” With the addition of religious righteousness, enslavement and maltreatment of other human beings became nothing more than another expression of God's good work.
But these days, now that Whites have lost some power to minorities, they can no longer reserve that civility for other Whites. In many cases, false civility toward non-Whites is now a necessity too:
Gone are the “good old days” for White racists, when they could randomly hiss scathing racial epithets at any old Black person anywhere they went, all day long, then turn to their White child and find a way to chastise her for “not watching her manners”. Now, many racists feel forced to act polite in at least some situations, or risk getting called the “r-word”, not just by someone Black or Asian, but by someone White. These days acting openly racist could result in vocational or even legal consequences, unlike the days of Dixie.
Still, instead of acting outwardly racist, some people will smile through passive-aggressive language instead, trying to appear outwardly civilized while saying mean things. That person is hoping to trigger a negative outburst, so she can pretend she said nothing wrong and tell herself that person's reaction to her was uncivilized.