>>53103969They can, and they do whenever they actually feel like it.
The fandoms are largely incompatible though, and even when they don't clash naturally, it's an easy mark for a shitposter to spark something. There's absolutely no way to avoid this and nothing that can be done about it. The only way it can ever get better is if we eventually reach some sort of tacit agreement were we all treat it as a meme, like what happens with rivalries between foreign countries and shit.