An essential part of civility is pointing out acts of incivility.
In contrast, many moderns seem to believe that merely acknowledging the possibility of incivility, is itself the height of incivility. But that's nihilism, not civility.
If you don't curb incivil behavior somehow, you are effectively encouraging it -- that's because often they have something to gain from it. Despite morals and goodness of people, if something incivil unequivocally leads to gain, it will become the norm. A social backlash is a collective way to fight it and align the ethical with the "rational" (in the many situations where the law isn't applicable).
Now that I think about it, there's been some interesting research that explores where the threshold for such flip-flops in mores are; but I have no handy link to that. Anthropology has shown that some societies which value viciousness and cheating exist and are stable. I gots no handy link for that, either, however.
In contrast, many moderns seem to believe that merely acknowledging the possibility of incivility, is itself the height of incivility. But that's nihilism, not civility.