He's a tape-recorder.. with no take-up reel; his auto-speech controller allows him to take ANY [subject] and invent a response-of-the-moment [predicate].
I think this may be {one hopes...} a unique brain-malfunction (and that's why there's no psych. data). Surely this Needs a NAME.

Any suggestions?

1) Myocranial Infarction?
2) Chronic Unfathomable Neuronal Testiness? (makes an appropriate acronym)
3) Weaponized Incoherent Nastiness Disease/Brain Accumulates Garbage
4) Fabricate medicalese: "One's BS-detector becomes a BS-generator".
... but these aren't very good.