There exist terrible ideas that society recognizes as terrible, like racism. There also exist some small number of people who cling to terrible ideas (like racism).
Because there is widespread agreement about the horribleness of racism, racists pay a pretty hefty social price for their racism. Almost no one wants to be friends with, associate, or even spend much time talking to a racist. Consequently, racists are motivated to conceal their racism.
Since there’s a high social cost for associating with racists, not to mention a generally icky feeling, many people will be vigilant for signs that the people around them may be closeted racists; at the same time, people will try to avoid behaviors which could be construed as something a closeted racist might do.
This, in turn, motivates closeted racists to up their game. Leading to even more scrutiny of people for hints of racism. As the arms race goes on, the threshold for “suspected/probably racist” gets lower and lower, leading to an increased rate of false positives, and eventually you get #cancelcolbert.
(Not to mention that during this whole process you should expect to see the already-small number of racists declining pretty rapidly).
The end result is that there’s pretty much no overt racism ever (yay!), but everyone is constantly afraid of being suspected of racism (boo).
Repeat as necessary for any widely-despised meme. Note that the criteria is being considered terrible by society, not actually being terrible. When non-heteronormative sexuality is subject to mockery and ridicule, you get (1) lots of guys saying “no homo” and (2) more people choosing to keep their sexuality a secret.
tldr: Signalling is complicated.