This would be sort of a death blow to much of postmodernism, no? "Reality is structured like a language and the free play of symbols reigns over all"-style thinking was very popular at one time, but this would rule against it.
But they mainly influence people who are not thinking to begin with. Or, to put it more mildly, do not have time to think about every issue and therefore adopt the current mainstream propaganda.
So in the sense "Can we conjure up a fake reality that many people will believe?" they are right". In the sense that "language is reality or even thought they are of course wrong.