I totally get it and I understand the need to vent about something like that. RPG groups can be so annoying when someone tries to control a group like that, from what I've heard. I also know that for the Pokemon fandom (all fandoms, really) there's a tendency to want to gatekeep others from participating in groups if they show an interest in 'shipping' or NSFW stuff because it's a common thing to see "Shippings RUINED this fandom!" Now, personally, I think it's more an issue of writers in general just not knowing how to make committed relationships interesting without making the characters a-holes, but that's a different discussion.
My take tends to be that you don't fight parts of culture that you don't like by screaming at those people and ostracising them, you fight it by making other parts more appealing. I mean, if you don't want people drawing fanart of Gardevoir, don't ban Gardevoir art or make people feel bad for making that kind of art, give them incentives to do other things, otherwise you end up with a paranoid group whose identity is "WE'RE THE NORMAL ONES," while the weirdos will start their own group and likely become the face of the fandom because, well, they're just more interesting than the 'normal' group.
It's an issue with internet platforms in general that should be addressed that it's just easier to get rid of people than it is to try to guide them down a better or more socially-acceptable path. I get it since if you're a mod and you see someone making everyone uncomfortable and you message them privately they'll be like "What?! No, I'm not doing anything wrong," so you need to either be tactful and be prepared to deal with a disagreeable person who thinks they're in the right, or... just click a button, ban them, and never have to deal with them again, hopefully. I don't know for sure what you did or didn't do, but I do hope that things eventually start going better for you and you find something that makes you smile.