It's funny when these great English minds always slagging off foreigners and tell them what they can do and what not.

So many comments like this I see every day on Twitter. I mean, come one, it's not a stone age. Football is global.
Context is everything. As a standalone comment, I agree with you. Football is global, and there's nothing wrong with that.
Context
It's annoying when 'fans' from (e.g. USA) pick a team to support and act up. There's no decent sides within a 1,000 miles so they look overseas. Let's say they choose Real Madrid or Bayern Munich. Just for argument's sake, because they're both odious clubs. So it'll help make this story more relateable. Bear with me here.
Then said American Real Madrid fan bigs it up on the internet, at work, wherever. Shitting on everyone else's team. Being an arrogant tool. Feeling smug in his reflected glory, which he had zero part in creating. And with months, and not years, of emotional investment. All the highs, and minimal lows.
When you're from somewhere where your
from down the road team is Elite level in global terms, but not necessarily of THE Elite. A local side who you go and watch live, and pay good money to do so, with little option to change your allegiances, because ... well because you just can't. Well, it's annoying when the non-Spanish speaking Madrid keyboard fans of this world act up.
They guy in your twitter screen grab probably wasn't one of those types. And the over-reaction not really necessary from the respondent (although I can't see the full conversation, so maybe it was). But it's not just English fans. Spanish, French and Italians can all be like this sometimes, it's just their tweets/posts etc don't get as much coverage because they're not in the global language, i.e. not in English.
To end my little story - this is why I engage here. Because most (*cough* Badass *cough*) of you global fans of Juve are not like the global fans of Madrid, Barca and EPL teams. And perhaps this is why the tweet seems as if it came from the stone age.
Take in the context. The West Ham fan was possibly from East London. Probably over-reacted, but may have had years of this crap from 'Liverpudlians' or 'Mancs'.
TLDR: two different types of fans, they'll never see eye to eye. It has nothing to do with nationality. The same response would probably had been given if the guy from Azerbaijan was from Cornwall.