I can't remember exactly where I saw it, but I have the tickle of a memory regarding something about it being a sort of religious issue. The inference I made reading something was that it was Nonman heresy. More specifically, that the Aporos was a rejection of mainstream Cunoroi spirituality, or their notions of the gods and Outside and stuff.
That and they were filthy traitors.
Probably it was some entry in the original PoN glossary, since none of this stuff was ever clear to me, at all, in the story itself.