I get the feeling that football in England is perpetually trying to balance tradition and progress, since pre-globalization, traditions associated with clubs were a big part of your fan identities.
Now that the sport has gone global, some of those local traditions will either be undervalued or misrepresented by foreign fans. Most local fans seem to be okay with this, and welcome new fans and gently correct anything they get wrong, but there is certainly a large portion of fans in football related subreddits who resent this invasion.
These latter group of people want their club to become a continental or global power, afford 100 mil+ players, and yet maintain the atmosphere that comes from being a local club which is part of a closely knit community. I get it: they grow up in a peer group that includes lots of fans of local clubs, for example Arsenal fans go to school with Leyton Orient fans, so there is a weird mix of community fandom and global fandom, and their peer group teaches them that anyone who doesn't attend every game is a plastic who can't know what it means to be a real fan, and I see that opinion parroted all over the place here.
The worst of the abuse is directed at American fans, followed by Asian fans. South American fans seem to be a-ok though, because their countries also have a footballing culture. Mostly some new unsuspecting fan says something which is anathema, for instance "guys I made this new chant!" without knowing that such a thing is considered an "embarrassment" in the local culture of the club, and suddenly everyone is on him like a rash because "dumb Americans aren't serious fans" and are ruining what it means to be a fan of the club; it doesn't matter to them that the guy watches all their games at 4 a.m. from the West Coast and buys merchandise and follows the club fervently despite the random abuse he gets from fellow fans online.
Most such cases I see here are from holier-than-thou fans who think they know best how everyone else should support their club. their opinion is irrelevant. The best solution is to stop giving a fuck what other fans think and support your club.