I'm unsure if anyone has approached it from this angle, but from what I've experienced as an NTR hater, is simply because it's polarizing.
In the past, there wasn't anyway to exclude specific tags during searches. You could include tags, but not exclude them. This created a weird dynamic where if you search tags you do want, you'd sort of be forced to wade through content you didn't like. It resulted in people discovering games they thought were interesting, but didn't notice the NTR tag and were blind sighted.
Plus, there was a very brief time period where NTR fans were very vocal. I remember seeing random comments popping up from people asking for it to be included in games without it. Some developers actually listened to those fans, and a very small minority of games added NTR in a random update (I don't remember the games anymore, they're likely all dead anyway.)
NTR haters began to crop up as a result of all of this. A bit of paranoia sparked, and anti-NTR became a massive trend. There were also several large-scale arguments cropping up on numerous threads, mostly due to trolling, but there was also some NTR lovers who would also fan the flames.
Throughout all of this, the 'neutral' people started to despise NTR haters. It became 'popular' to be an NTR-hater hater. This further fueled the discourse, and while most of the NTR lovers had mostly became silent, the NTR-hater haters began to further fuel the arguments.
NTR-haters felt like they had become the #1 enemy of the forums. They grew more extreme, and the more people pushed back against their ideals, the more extreme they became. It certainly never helped that as a community, we could never come to an agreement on what "NTR" actually means in the first place, which only caused more arguments, even amongst the NTR-haters.
Meanwhile, outside of the adult gaming community, the NTR genre was growing in popularity. Rather it be hentai, or mainstream porn. Then the black/red pill crap started which only aggravated everything in the community even further.
So anyway, this is the origins of the communities NTR thing. At least from my perspective.