That's because slander non-stop, the kind of slander you people dish eventually just gets tiring.
Coming into a fandom and liking a particular character, start drawing or making threads about said character to show your enjoyment of it. And here comes a troll talking about the character as if they have to be their personal bully every. single. time. Every time you point out some cool thing the character did, here comes that person downplaying it, and even going into disgusting gross perversions of the character, making art of taboo subjects and claiming the character participates in them.
We're not talking a few trolls here and there, but a constant morale breaking harassment of it.
But while doing so, those people trump up their character, talking about how they're so great and even saying they'd kill the character you like. Eventually the mind gets fed up, and starts associating the character to the trolls, and hating on both.
I've gotten to the point I wish Zoro to miraculously fail and even hopefully die just because I want the agenda slanderers to STFU and be humbled for once in their god forsaken life.