It is of course a common and effective rhetorical device to frame oneself as divulging information they don't want you to know- quite a few bestsellers are made this way. But there is no concerted effort today to bury Epicureanism. Both scholarly and popular treatments of the philosophy are readily available and work continues to be done on the Herculaneum papyri and other material. I don't really see how the moneyed rulers of society really care about one philosophy over another. The primary enemy of Epicureanism, from a PR standpoint, is indifference, as it is with a great many beautiful things.
I would also question the treatment of Plato's Republic as a literal and dogmatic blueprint for how society should be formed. The subtleties and difficulties of Plato's work really don't justify broad statements like "Plato is a proto-fascist." One can find much to critique in his work without doing that. The one very committed, self-declared neoplatonist I know is an anarchist labor activist. The story of Plato wanting to burn Democritus' books is just gossip like so much of the philosophers' biographies.
Lastly it's unfair to say "their notion of atoms... falls far, far short of today’s knowledge" because what modern chemistry/ physics calls "atoms" are by definition not the atoms that Democritus et al were talking about. Maybe we should call them "toms" instead.