People who are proud of being part of "the official fan club" or "the big fan club" are pathetic. Like dude, you are not any more representative of the community or the original work itself just because you are a self-important Karen.

Yes, this is the correct application of gatekeeping. Sure the big guys have a right to gatekeep and try to keep the fandom pure (let's ignore that they've already been coopted in this example), but the flip side of that is that people who don't like it can make their own groups with their own rules and then they keep out anyone who they don't like. This is not totally unlike capitalism and the creation of new companies that hire more employees. It ensures competition and demonstrates that nobody "owns" canon. More groups for everyone makes a vibrant community - NOT trying to create a super club that appeals to the least common denominator. NOT saying that you're the main fandom and then trying to squash all competition. The more the merrier - most people would be fine with a "LGBT queer themes in Tolkien fan club" existing as long as they don't have to be a part of it.

I think I'm preaching to the choir here but just wanted to put it to words.

How many things have we seen when certain "important in fandom" types bullied others, abused them, scammed, started witchhunts because of petty reasons, etc.?

Fanboy culture yeah, same thing we see in console wars or even here when we argue the merits of a particular game. It's fine to disagree but people take it oddly personal when you don't like the same things they like.