I still think the greatest example of irrational shipping hate I have ever seen and maybe will ever see is Matsuri from Naruto.
Matsuri is an extremely minor character. In canon she and her friend Sari only really exist as an example of how Suna’s attitude towards Gaara has changed over the timeskip by being two chunin with crushes on the Kazekage and then just mostly background stuff, a few lines here or there. All her other appearances are in filler arcs. And she’s gotten solid hate since the first one.
What happened in that arc? She was an academy student who picked Gaara as her teacher since he went to say something to her but stopped talking when he noticed he was making the other students nervous (this is after all, pre-timeskip Gaara) and she wanted to know what he had to say. We also get some irony since due to her parents being killed in front of her Matsuri is terrified of weapons (yet still wants to be a ninja and protect people) and the person she picks as her teacher is a guy who was literally a living weapon. Matsuri is then kidnapped as the easiest person around Gaara to kidnap (given she’s an academy student while Temari and Kankuro are bamf!chunin) and we get a fun teamup arc with 10 of the Konoha 11 while rescuing her and thwarting a plan to weaponize Gaara/Shukaku. Outside of her intro and providing a bit of help near the end she’s almost more macguffin than character.
And for some reason people just lost their freaking shit about her. Like, she’s the closest thing Gaara has to a love interest (I guess) but again, it’s almost all filler so just ignore it if you dislike her character for whatever reason (now that I’m older I’ll admit her dub voice is terrible and I dislike it). Ignoring her is the easiest thing in the damn world to do because she barely has a presence.
And she’s gotten a couple more fillers. One was just her in the chunin exams along with two teammates, which wasn’t even focused on her but the exams and all the other genin in them (there’s another important Suna genin Gaara taught and several of the Konoha crew and Fu aka the seven tails host) and she’s in an expanded part of the war arc where they just added some extra scenes to fights. Like she actually gets some cool moments, but if you hate her, hey, it’s all filler anyway. Ignore it.
Yeah no the “die Matsuri die” feeling is still strong. There’s a whole club for it over on DA, too, has been for nearly a decade at this point.
Here’s the thing that pisses me off the most though. The people going “die Matsuri die”? Yeah they often use Sari as a possession sue, either to help in offing Matsuri, get with Gaara herself, or praise the ship the author likes with Gaara as “obviously” Matsuri wouldn’t care if her sensei was happy but Sari (who unlike Matsuri has no characterization outside of a crush on Gaara) is somehow okay in their books? I mean at that point it’s not even about shipping anymore it’s about hating Matsuri for the sake of hating her. And it’s going on to this very day!
And again, it’s all just so unnecessary. Like, even by shiphate standards it is entirely unnecessary, she’s not someone like Sasuke or Hinata or Sakura you can’t just leave out of the story--you totally can! So yeah, anyone who ships Gaara with someone else can just...ignore her entirely. Bringing her in to bash her only says “friendly reminder: I so irrationally hate this mostly-filler character that I am going out of my way to include her just to do her harm.” It’s pretty much admitting that she’s a memorable effective character since they just can’t get her out of their heads. But it’s also really depressing since, well, female character who’s done very little gets hate just because they’d rather ship her male love interest (and again, she’s not even really a love interest to Gaara, just the closest thing he had until Gaara Hiden came out) with someone else and that means Matsuri must die. It will always be one of the greatest wtfs of my fandom experience.