But not all children can be relied on to demonstrate this native moral purity, because if adults are corrupt, then surely some of their corruption will have rubbed off on their children. So it is only children who are somehow insulated from adult influence, and by extension from civilization, who can remain pure: orphans like Huck, or virtual orphans like the reformatory boys in Nip the Buds. Such outcast children appear to polite society as uncivilized and wild, but this is only because the adults have the wrong perspective and don't see that it is they who require civilizing. What they perceive to be wildness is in fact natural morality, to which they, in their gross immorality, have become blind.
To accept this device, you have to accept some version, religious or secular, of the view that children are born free of sin. And there are secular versions of this and its opposite: Hobbes and Freud are modern, secular proponents of children-as-sinners, at least in the loose sense that this kind of literature requires. They view the child as the father of the man, and the disorders of civilization as contained in miniature in the primitive, unrestrained passions of individuals. The Hobbesian, Freudian argument of Lord of the Flies is that the source of injustice and disorder is in our nature, and that the artifacts of law and government - adult artifacts - must be imposed on that nature in order to suppress or channel our innate tendencies towards injustice. Nip the Buds, and to some extent also Huck Finn, follows from the competing premise - that the child is naturally moral (and further, natural morality is good), though susceptible to corruption by adults. But where adult corruption has grown very great, we can still turn back to the instincts of children to guide us back to our natural state of goodness.
I am at best ambivalent about this device. Empirically, I have little doubt that it is wrong, and that children (especially children in groups) are not naturally or instinctively good to others or one another in the absence of adults. But it has some literary merits: emphasizing the purity and innocence of childhood adult political injustice. And even Oe is not fully Rousseauian: in the end, the idyllic mountain-top commune of reformatory boys commits injustice when faced with the prospect of death. Still, it is a device based not just on a kind of noble lie about childhood's goodness, but one that potentially distorts the truth about nature and morality in order to heighten the poignancy of certain political injustices.
Also, I don't think I've ever read a modern parable of this sort - set somewhere unknown, taking place outside of time, populated by unnamed and half-drawn characters who represent moral ideas more than actual people - that wasn't, at bottom, kind of schmaltzy. The Lottery, The Ones Who Walked Away from Omelas, The Plague, even Animal Farm. They're engaging, intriguingly ambiguous, highly-assignable course material to get students thinking about political theory without realizing it. But because they're ambiguous and sketchy, they always seems to end in an edifying condemnation of injustice arising out of a totally ungrounded hope that society could be better if we just put our minds to making it so. But things can't always be better, especially if the injustices are part of us or inherent in living together, and not just the unfortunate imposition of particularly horrible grown-ups.