Sigh, way to miss the entire point of what I said. All the modern mindset of how humans are so enlightened is a badly fabricated illusion that comes undone at the slightest scrutiny.
Our prefrontal cortex which pretty much makes us the most successful animals on this planet, is a couple of million years old, in evolutionary terms it's an eyeblink. Our lizard brains? billions of years old.
And here is the kicker, all our impulses and emotions get filtered first through the older part of our brains, way before it ever reaches the more modern part of our brain. We think we are in charge of our emotions and reactions, when in truth it is the other way around.
The primitive part of our brains, does not factor in things like relationships or morals or any of that stuff, it is what it is, and it is the most violent animal on the planet, that make chimpanzees (you know the things that will bite your face and dick off, and proceed to eat you while you are still alive for the sheer amusement of watching you suffer) look as cuddly teddy bears.
We are absolute monsters when the masks come off. And I am not condoning it.
To our primitive brains, if women are in your immediate surroundings and you interact with her on a regular basis , she is a mating opportunity, end of story .
Barring familial ties, and in many cases even that does not count. Incest is real folks. Statistically, a good number of us somewhere in our family tree, especially if you go back far enough, have an ancestor (more likely several) who was born of incest, and/or rape as well. Either brother sister, or father daughter are more likely, but son mother also happens sometimes.
And again I am not condoning it, it is what it is, reality is a fucked up place sometime. Just look up the Japanese unit 731.
Any other male trying to interact with her is a threat who is trespassing on your territory. Modern morals do not factor in.
Ntr is hated because it puts you into the shoes of a man so stupid and so spineless as to not be able to or not willing fight off, or even worse, be condoning of other men encroaching on his territory and fucking his women. It is a deep instinctual response that we have no control over.
It's not rocket science. Hell imagine an ntr story, where everything proceeds in the old cliche way right up until the guy finds out what has been happening, at which point he castrates the guy fucking his woman with a rusty spoon, and sodomizes the slut with a horse cock dildo so badly she will be wearing diapers for the rest of her life. Sounds like a shit story? Yeah it is, but I wager, ntr haters would love the story.
Because it gives the mc some agency to react to and win back some self-respect, rather than relegating him forever to the position of spineless coward.