Stranger in a Strange Land is fiction. Obviously it’s possible to write about the idea of a religious cult that is a great vehicle for rationality, but it’s equally possible to write about faster-than-light travel. Do you know of any real-life examples?
My experience suggests that even religious organizations that purport to venerate rationality (Objectivists, the Roman Catholic Church, possibly the Pythagoreans) are less effective at promoting rationality than other kinds of groups. Objectivists ended up being downright insane.
The AI is communicating in a perfectly clear fashion. But the human’s internal inhibitions are blinding them to what is being communicated: they can look directly at it, but they can never understand what delusion the AI is trying to tell them about, because that would shake their faith in that delusion.