The explanation is simple:
in normiespeak, the script language the NPCs are programmed with, the word "incel" means "anyone who disagrees with me or insults muh qweeen".
They can't intuitively make distinctions between different classes of ideas, or groups. They only operate in black-and-white, in terms of "us and them".
The programming is this:
Ideas corporate medias says I should agree with = basic human decency.
Ideas that disagree with the corporate dogma = bad, incel, nazi, racist, "do you have a source for that?", homophobic, misogynystic, bigoted, anachronistic, "snopes already debunked that", sexist, denialist etc.
The normie NPC can't comprehend that there are often dozens of well-thought-out, well-sourced opinions on any non-trivial topic (e.g. human mate selection). To the normie, there is only the "basic human decency" (corporate brainwashing) and the "fascists" (everyone else).
Maybe a psychologist or social engineer would say this is due to an incomplete separation from the parents. The child initially believes his father is omniscient until it discovers he's not. The NPC seems fixated in the delusion of an omniscient father-figure from snopes, or corporate media that will supply all the correct answers always, and everybody else is an incel nazi.