The problem with fandoms as a concept is that they're inherently tribalistic and myopic. A lot of people think that joining a fandom entails signing some metaphorical binding contract: you must dedicate all your time, energy, and sometimes money into this fandom and you must agree with the opinions of the trendsetters (be they the people involved in making the work the fandom is based on or the highest profile fans), and you must despise any and all of this fandom's agreed-upon boogeymen, lest you be cast out of the group. As someone who's always had fairly diverse interests, I've never really clicked with fandom culture for that reason: In the real world, no one's stopping me from being interested in, say, Pokemon and Wicked and Red Letter Media. I can explain to you the plot of Kingdom Hearts but I could also spend the same length of time explaining to you why Sunset Boulevard is the greatest film ever made or I could talk about this new eyeshadow palette I just bought. But, really, any one of those fandoms (except maybe the RLM crowd) would shoot me weird looks at best and rant about why my other interests are terrible and a waste of time and that I'm a fool or a traitor to the fandom for liking them at worst. Even quote-unquote "normal" people that I meet in real life usually have trouble understanding why my Spotify playlist simultaneously has modern R&B and classic rock on it. A lot of fandom people think literally any other thing you can spend your time on is a dangerous threat to their fandom, and aren't open to the idea of people simultaneously enjoying it and one of the fandom's nemises (I've heard this complaint a lot from people who simultaneously like some part of nerd culture and professional sports, a classic non-dichotomy people continue to insist is one. The jocks have mostly buried the hatchet with nerd culture, it's the nerds who are still hostile.) It's tough to say which fandom has this problem the most, but cartoon people (especially fans of modern Western cartoons) see literally anything that's live action as a threat to their precious animation, and anyone who prefers live action works over animation is a cultureless pleb. The worst parts of the anime/weeaboo fandom is similar in that even the worst anime is still superior to the greatest Western masterpiece. And any fandom with a strong superiority complex (*cough*Rick and Morty*cough*) get a kick out of putting down stuff they view as unintelligent.
TL;DR - don't be a dick to people with different interests than you. Pretty please.