People usually arent rational though. Its unfortunate, but the rule of 'its fine when i do it' applies to nearly everything in real life and of course to fetishes like ntr.
Its why alot of people love netori, while hating netorare. To them its one MASSIVE power fantasy, they are the ones with the large dick, endless stamina and the ability to get an harem of girls who praise and devote themselves to him. Netorare however, is a blatant threat to this power fantasy. Because it reminds them of reality. Its why its so reviled compared to other fetishes, it brings forth their weakness and insecurities, and they loath to face or even acknowledge.
Honestly, its fine to dislike netorare, be it for personal reasons or simply not liking the fetish. And a healthy discussion over it can be fun with those that dislike it, like are harems a big ntr sharing circle or not.
But dont expect that from everyone, there are maniacs that truly believe they are in the right and are justified in their actions. Just don't lump everyone that dislike this fetish with these hateful fuckheads.