You'd be surprised, it's not quite as guaranteed as you think. Look at the current U.S.A. political situation.
The fundamental difference here is that I think you can have your traditional lifestyle. In fact, I'm #TRADLIFE myself. I want a white husband, a dog, a picket fence, and to watch Leave It To Beaver right before supper time every evening. Sounds awesome.
The thing is that I want everyone to do whatever they want. Having groups and samey places is fine, look at chinatown or little italy in New York, for example. You can have your places where you feel at home if you want to.
The issue is the connection between purity, nationalistic ideals, and imperialism. Which is the main divide. I don't care what other people do, whereas a lot of nationalistic people care really really much about what others do and try to force them to either assimilate entirely or GTFO. Having safe spaces is what everyone deserves, I just don't think we should be entirely isolated from the other. Living your entire life in a chinatown like location would be damaging, but having that place to retreat to when you want to is nothing but cool.
If you want anything you should be able to achieve it, just so long as it doesn't hurt others. I don't really think entire countries being ethnostates is a great idea. I'd be down with smaller and more diversely placed styles of similar locations.
I also think that hating the other is something we shouldn't do. Let them chill over there, let us chill over here.
Of course, with our current era of extreme displacement, refugee crises and so forth, things get muddied up. I think it's fine if people don't want entirely different cultures running all over them so fast, but to outright reject them entirely when they don't have a home to go back to is just fundamentally unfair. This would all be solved in a globalized society, where everything is laid out in fair and equal ways. I think we can achieve a fractured version of this if we end the awful wars in the middle east within our life-times. I wish displacement and refugees didn't exist. But instead of rejecting and punishing them, we should work on helping them have places they feel comfortable going to.