Humans are social animals, and like to know they're doing the "right" thing, where "right" is often defined by what everyone else is doing. A common example of this kind of "social proof" is a counter productive littering campaign that told people that everyone was doing it. So people thought, well if it's good enough for them.

It seems clear to me that people don't like being called racist. So much so that they'll try really hard to convince people to stop calling them racist, by threatening to do more racist stuff if they don't. Probably, though they don't like to talk about it as much, simply the threat of being called racist hold them back from doing racist things.

This theory is also corroborated by the number of people who suddenly felt their xenophobia was widely shared and that they could therefore attack random people after Brexit or Trump's victory. Literally often prefacing their behaviour with the announcement that it was now okay.

I have to admit I don't know with certainty if it's productive or not. But if the people saying it is are mostly concern trolls, then I'll take a leaf out of their book and reject it just because I don't like their tone.