If they do realize that, then those who *use* the "dog whistle" as the basis of their complaint are probably just projecting their own faults against those they hate. Check out some info from psychologists who've had it pegged for a long time: Projection & Deflection--Projecting one's lawn faults onto someone else in order to cover up that fault in themselves.
It's been Radical Leftists saying "This is a dog whistle," "That's a dog whistle," pretty much always saying it against conservatives & large groups of the population that they don't even know anything about. The people who are being *accused* of racism, xenophobia, nazism, etc. don't even know anything about the "dog whistle" that the Lefty is using to accuse them...But we certainly hear the "dogs" barking out *about* the "dog whistle" even if we can't hear the "whistle" itself.
So if it *is* just another baseless conspiracy theory, it's the Lefties who make all of those "dog whistle" accusations that are the ones who made it up.