Someone from Iran said this... pretty damning.
"We just need to stay separate, all this diversity is just pure evil designed intentionally to make us despise each other, we have a saying in Persian "Druio Dusti", which means "staying apart means staying friends", Iran is the only historically diverse nation with something that could be considered, admittedly with some generosity, "success". We should stick to our own. Our own blood, our own land, our own traditions, our own religions, our own food.. A little bit of diversity as a traveler is great but what's going on in the west is just pure evil, for everyone involved.
I went to London to study 12 years ago and it was so unpleasant that I returned to Iran after I got my degree even though I had a job offer there. People here thought I was insane, leaving Europe and returning to a heavily sanctioned Iran, but I wasn't, I realized that there was something dark and sinister happening in that city, people treated it with utter disdain, the locals hated the newcomers and the newcomers hated the locals, and they took out their hatred on the city infrastructure, so everything was grey and ugly, and everyone was angry and ugly, you couldn't smile as that would have been considered a sign of weakness, I knew it wouldn't be long before they started taking all this frustration on each other.
I saw more Burqas in London than I ever did in Iran. I saw more radical Islamists in an average London mosque than I saw in a pro-government rally in Iran, and everyone treated everyone else like crap. All of this was the result of diversity. Even their Islam was disgusting and corrupted and rotten to the core, emptied of all traditions and history, just one more thing to use to mess with the locals. There was an Irish fellow I befriended who told me that he had been bullied throughout his school years by Pakistanis and Arabs, he said they always had a gang mentality and had cousins and brothers to join the fights, so they always won. He told me this was a common occurrence. I used to wonder how brainwashed and weak these people are that they're just taking all of this.
Their rulers hate them, but they hate us too, to them we're just tools to use and weaken their own people, after the second world war European elites got scared of a revolution by their "uppity" peasants, and so they decided to bring in a new peasant class. After seeing how they've dealt with their own local peasants, do you want to be a part of their new peasant class? I didn't."
I do find it interesting learning from people from different cultures and backgrounds. But I don't need to be in a diverse class.
It would be different there, and you don't really want to be learning with criminals or people who have no problem with violating your boundaries because that isn't a part of their culture.