Yes, I have been on both sides of this a lot -- I'm a major OTPer, I'm a villain fan, I'm a crazily sensitive writer; my fannish feels get hurt by all manner of things. And in some ways it's...not worse, but maybe differently bad, when it's about things like character tastes. When it's an actual trigger, there's no shame (or shouldn't be) in admitting you are taking real psychological hurt. When I'm hurt because someone doesn't love my OTP, that's...it makes me feel absolutely ridiculous and silly but at the same time I can't turn those feelings off (and wouldn't want to, because they bring me joy, too, even if I feel silly about that too sometimes! ^^)

I'm trying to be aware of that one both sides of the coin.

This, oh yes, this -- positivity can be painful too; people joyfully shipping a NOTP of mine can make me go GRRRRRR but the harshing squee isn't worth it. Though sometimes it can feel pettily good in the short-term, in the long-term I end up feeling like a dick (because I maybe am) so...

(...ahahah now I'm so curious about your disliked NiF character. I love just about everyone in that show so probably don't share it but then the part of me that enjoys wank is all ooooh ^^;)

And yeah, I've hurt people -- I do love a good debate and my friends mostly do too, but sometimes it can get personal without either of us even realizing it until there's real hurt. And you apologize and work through it, but it takes effort and trust needs to be rebuilt.
The fans I don't know that I've discouraged, they're the ones I feel even guiltier about, and I just can hope I'm reducing the damage as much I can!