If Plato, having set out to write about the theology of the Athenians, had felt disgusted at it and started to criticize it for containing internal dissent and parents having sex with their children or eating them, and for praising the punishments in revenge for these acts, exercised on their parents by children and by brothers on brothers and other such things; if Plato thus, having taken on such stories, had criticized them in public, he would, it seems to me, have given the Athenians a reason to show themselves evil again and kill him too as they did Socrates. Because he would not have chosen to live rather than to speak the truth, and because he saw that he could safely reconcile living and speaking the truth, he put Euthyphro forward as the personification of the Athenians, a pretentious man and an idiot, who thinks wrongly about the gods as nobody else, and confronted him with Socrares himself in his usual way of acting in which he used to question everybody with whom he was discussing.--Numenius, On the Secret Doctrines of Plato (fragment 23), translated by Peter Van Nuffelen in Rethinking the Gods (74).
With the revival of fortunes of murderous religions and the accompanying rise of the data-mining, national security state I expect that interest in esoteric doctrines and dummy doctrines to rise as well. For, the art of reconciling truth-speaking with living is in high demand when one can be killed for one's views* or receive a one way, lifetime ticket to one's local Guantanamo Bay based on secret intelligence. Some such deeds -- e.g., Socrates's death -- are legally sanctioned.
In the quoted passage, Numenius treats Plato's Euthyphro as a "theological treatise" (Van Nuffelen, 74) in which Athenian popular theology is criticized indirectly. It is endemic of the disdain for Straussianism and anything having to do with esotericism in professional philosophy (recall and here) that the Stanford Encyclopedia article devoted to Numenius, treats the fragment (one of the few surviving ones!) in a single, passing sentence. The Euthyphro is traditionally "classified as Plato's first work....Numenius' interpretation of it, as a hidden refutation of Athenian religion, implies that Plato, from the outset, chose to conceal his true doctrines, or at leas those that would seem offensive to the Athenians." (Van Nuffelen, 77) Given that many of Plato's dialogues contain doctrines that are critical of the Athenians, one wonders how on Numenius's account, the distinction between, say, mildly annoying to and dangerously offensive to Athenians was drawn by Plato. Perhaps, Numenius thought that when Plato felt "disgusted" by popular opinion (note the relish with which Numenius describes incest and cannibalism), he had to be careful to state his own opposing views. (Numenius may have been guided by reflection on Leontius's reaction upon seeing "the corpses that lay at the place of public execution" in Republic 439e?)