These days, forcing the boys and girls to "share" and "get along" is called "multiculturalism." It has never worked in the past, anywhere. It doesn't work now, anywhere, and it won't in the future, ever. There are many reasons why it doesn't work, but I think the simplest is what I will call the Tribe, the Outsider and the Scapegoat.
Human nature is such that people instinctively gather into tribes. Every living creature, from ants to elephants, does it; why should people be any different?
This tribalism is a problem that will never go away, so there is no way around its existence. People want community, and that community usually involves being with people like them, or who they like. This has to be dealt with, which is something libertarians rarely do because of their obsession with "the individual."
"Tribes" may be a primitive term, but it was applicable not only in the past but also certainly today. You might want to call them "ethnic groups" or "nations" instead. It doesn't matter. They're still tribes, whether they're big or little, powerful or weak.
Problems arise because every tribe in the past has, with monotonous regularity, because of our inborn narcissism, grandiosely called themselves “the People" or "the Humans." Anyone outside the tribe was, obviously, devalued into being non-People and non-Human. That gives a foot in the door to murdering them.
All tribes today still consider themselves "the Humans," even though they use different words. No country today is going to call itself "the United States of All Humans" or "The Union of All People, and Everyone Outside Isn't," but all countries will say God has chosen them and is on their side, which logically means the Other Guy is on the Other Side. That's pretty much saying the same thing as "We're human, and you ain't."
During World War II, for example, the Russians spoke of "Holy Mother Russia;" this implied that God had chosen Russia. Their opponents, necessarily, had to have the Devil on theirs. We're the People; you're the Unpeople!
Their opponents, the Germans, did the same thing the Russians did, when they talked of the “Fatherland” (and today, for us, ominously, it’s the “Homeland”).
German soldiers used to march into battle with “Gott mit uns” on their belt buckles. I suppose it was a magic talisman to stop bullets. The question is: on whose side was God during the battle of Stalingrad, where both sides lost, combined, more soldiers than America has lost in all of its wars? The answer: neither.
It's painfully obvious that a grandiose certainty that God is on your side does not equal God being on your side, even if Jerry Falwell believes it. Neither does it mean your tribe is human and the other is not, even if you think God told you that. A movie example that comes to mind: I remember watching a Japanese officer, in The Last Emperor, exclaim, "The Japanese are the only divine race!" Later, when Russian soldiers closed in on him, he scrambled his brains with a pistol bullet. Self-proclaimed divinity always has a price, never a good one.
People in the U.S., cultural differences aside, are in some essential ways no different than people anywhere else. All people have a shared human nature.
People ask, "God bless America." It's never, God bless another country; it's always, God bless America. God should keep America's soldiers safe, but never any other country's. Our soldiers should be saved by God; their soldiers should die. Is that any different than those German soldiers with their talismans? Why should God bless America if America does not follow God's laws? It should be so simply because we, in our magical thinking, believe it should be so?
It's all pretty grandiose. It's assuming Americans are the Chosen, just as every tribe in the past has thought it was the Chosen. They weren't, and neither are we. Other tribes are full of humans, even if we pretend they aren't and act as if their deaths mean nothing and are just the "collateral damage" that always happens in war.
The most famous, or maybe infamous, story about the Outsider and the Scapegoat is Shirley Jackson's "The Lottery," which everyone in the recent past had to read in middle school. Every year, someone was chosen as a scapegoat, which made them an outsider, then stoned to death. It was an example of scapegoating always leading to human sacrifice, of projecting "badness" on someone and then killing them, in order to "save" the tribe.
The human sacrifice in Jackson’s story was a fertility rite, which scapegoating and sacrifice always are: once we kill them, our culture will be renewed and reborn, since the “evil ones” will have been eradicated. This is why to the Greeks Dionysus was a fertility god, or why the Aztecs ripped the hearts out of hundreds of thousands of people. They thought it made their crops grow.
Since every tribe grandiosely considers itself "good," all "evil" must be projected elsewhere. If one tribe considers itself human and good and chosen by God, then the other tribe, the outsider, must necessarily be evil, sub-human, and of the Devil.
Maybe we don't consciously believe it, but emotionally we do. It why most people don't care -- indeed sometimes even cheer -- if foreigners die in wars. Then we act shocked when foreigners cheer when we die, the way some cheered about 9-11. How dare they act like us! Since we are good, they must be evil!
It was horrible that nearly 3000 innocent people were murdered on 9-11, but was it was a good thing the federal government murdered all those people in Vietnam, Panama, Serbia, Afghanistan and Iraq? But since they were outside our tribe, they don't really count, and sacrificing and killing them doesn't matter because it was to "liberate" them.
Today in the U.S. you can see our tribe projecting certain of its problems on the outsider. The U.S. attacked Iraq twice ago when it didn't attack us, then blockaded the country and killed hundreds of thousands of innocent people, then placed troops in Saudi Arabia, and supported Israel uncritically no matter what it did. We did this because we are "good," at least in our tribe's collective groupthink mind, if not in the mind of other tribes.
And since scapegoating and human sacrifice are always fertility rites, bombing and destroying other countries is of course supposed to make them be reborn and “grow” right – usually by trying to seed them with democracy and feminism.
When resentment, envy, anger and hate sent blowback our way on 9-11, we denied the bad things we had done to others, and instead claimed our attackers had to be "evil," and attacked us because we are "good." Maybe things are that simple in the childish, black-and-white fantasy of Bizarro World, but certainly not in reality.
It's bad enough to have different tribes in different countries get into wars, but when tribes in the same country war, that is a prescription for national suicide. And multiculturalism, if it is anything, is several ethnically-different tribes fighting over the same land and for political power, which is power over others. It is therefore an attempt at national suicide.
Each tribe is going to grandiosely call itself "the Humans" in some form, then deny its flaws and instead project them onto the devalued other, which it will want to remove or murder. Each tribe will also try to use other tribes as fertilizer, to make their own tribe and its culture grow and prosper.
Every empire in the past has fallen not because of attacks from the outside, but because of attacks from the inside. Once the barbarians are inside the gate it's harder to remove them. They may claim they're not barbarians, but apparently the Greek story of the Trojan Horse isn't taught to Americans in school anymore.
Some examples of tribal warfare? How about "Movimiento Estudiantil Chicano de Aztlan," whose motto is "Por La Raza todo. Fuera de La Raza nada." It translates as, "Everything for the race. Everything outside the race, nothing." That's clearly grandiose, and fits exactly the idea of one tribe denying its flaws and projecting them onto a devalued other. It is projection/scapegoating leading to human sacrifice. They're the cause of our problems, not us. Remove them or rub them out!
Another example in the U.S.? In the original teachings of the Nation of Islam (related to Islam in name only) blacks are gods, the original men, and whites are devils. Guess who's completely to blame for the problems of the former? You've got it. It's just another example of "Since we are good, you must be evil and the cause of our problems, so we must eradicate you." Denial and projection. Lies (to oneself and to others) followed by scapegoating and human sacrifice.
People will always define themselves not just as individuals but as part of family, nation, religion. If large enough different groups of people try to share the same land and vie for political power, each is going to define itself as good, the others as bad, then deny its own flaws and instead project their problems on those defined as outsiders. Leftists, who support multiculturalism, don’t merely misunderstand human nature but instead don’t understand it at all, not when they believe several large tribes can co-exist peacefully on the same land.
The only way different tribes can occupy the same land is if one is tribe is 95% of the population, and the other tribe is five percent. But three tribes that are each one-third of the population? There has never been a society in the history of the world that has survived such an attempt.
The problem is made far worse when the State gets involved, because each group will fight for political power to protect itself and hurt the other. Each group will try to capture the State to use for its own purposes, which involves removing the others, or, ultimately, killing them.
State-sponsored "multiculturalism," a misguided attempt to force different tribes to get along on the same land, will, as it always does when the State gets involved, have the exact opposite effect: it will make them fight even more, to the detriment of those involved, and, ultimately, the nation. Not only are the boys and girls not going to share and get along, they're going to get into constant vicious, bloody, murderous brawls.