I'll try to be blunt, but fair and empathetic.
Geno fans aren't really a pariah on other sites. Sure you'll find antis wherever you go, but the sentiment towards Geno fans is nowhere near as harsh.
Geno fans were also considered standard fair during the Brawl days and were even considered pretty cool in the Smash 4 days.
There was a big tonal shift in the Geno community between Smash 4 and Ultimate and it seemed to stick for quite a while.
I don't know what the exact cause is, but the thread did start to develop bad behavior and that solidified people's perception of the Geno's thread. There was little community policing and issues with leadership.
And yes I know there were people bullying the Geno thread, but the best response to bullies isn't bully back and yeah, snide comments in public forums do count as bullying. If you have to vent, it's the safest to do it in PMs with people you trust. Airing it out in public is how you get bullied more. That's not me trying to blame the victim either. It's trying to tell you how to avoid putting that metaphorical target on your back.
If I had to give advice, I'd say just focus on policing the community and finding a good, socially smart leader who cares for people inside the group and outside of it. It's real easy to make a community an echo chamber, but one should strive to ensure it doesn't happen because on the off chance the predicted outcome doesn't happen, it crushes you. Instead, accept the possibility that it might never happen and find happiness elsewhere. Speculation can be exhausting when you put your heart on the line. Find other aspects of the game or life that you like, or talk to others to find out why they like things you don't. You may even grow to like new things. That's the beauty of crossovers. There's always new stuff to learn about.
One reason the Isaac and K.Rool threads were so successful is because they have very level headed community leadership in N3ON and BKupa. The reason the Ridley thread failed in Smash 4 was because... it didn't really have a community built like that. It did, at some points, but things got out of control and it didn't last. A good way to tell if the leader will last is if people outside the group respect them. It means they have the social tools to keep the community safe, respected and respectful.
I don't want you guys to give up on a character you love, but if the thread wants to improve its reputation, some community restructuring is gonna have to take place. I'm not even gonna hope to suggest who should do that. It's something you guys are gonna have to figure out on your own.
But if the Ridley thread was able to pull itself together, you guys can.