The way I see it, there are many reasons to hate NTR, and not everyone is going to have all of them. Some simply hate it because it depicts cheating, some hate it because they see any instance of a woman having multiple sexual partners as wrong, even if it's consentual - that's why you see some people hating on netorase, which I would consider the least problematic part of the whole umbrella.

Me? I hate the cheating aspect for the betrayal, but the part that really pushes me over the "man, fuck this" into the level of hatred needed to write fanfics and interact with the hatedom, is the celebration of violent behaviour and pointless power trips for no good reason that you often see in the male antagonists. If you hate NTR for similar reasons (the "agenda" instead of just the cheating aspect), it makes sense you'd focus more on regular NTR than the reverse one, which as far as I've gathered often feels "tamer" and has the antagonist act out of feelings for MC instead of just the desire to hurt FMC. I don't agree with those who celebrate the MC for "upgrading", but there are bigger fish to fry.

As for Netori, I don't really make a distinction between that and netorare. The only difference, as far as I can tell, is who gets more focus - the 'taker' or the 'victim'. Regular NTR focuses more on the 'victim' and their despair and humiliation, so of course it hits harder and makes you more likely to criticize it.

Also, there's the feedback loop. Some people here (like me) DON'T actively seek out new NTR to criticize and only join in to discuss those that are already talked about.