Acting as if all people can be separated from their genetics because of an ideal is optimistic at best. Culture is downstream from genetics. You can not bring tribal elements into a society based on the ideals of logic and justice and expect the magic soil to change them. It does not. There is ample evidence of this. Your hope that it's true is not enough to make it true.

Cultures built on sentiment, will never embrace logic. They will always be tribal. Tribal survival is more important to them than justice. Logic is overwhelmed by sentiment. With jews, it's the fact that their father is Satan who is also the father of the lie. They are, quite literally, the people of the lie. How will you reconcile that with logic and justice?

>Identity politics is also incompatible with the cement that glues the diverse American polity together.

This is historically inaccurate

Until 1964 if memory serves, the US immigration policy was specifically designed to preserve a white christian majority. Jewish lobby succeeded at changing that, we see the result now

Besides, it is known since antiquity that ethnic diversity creates factions eventually leading to internal conflicts. Ethnic unity is far more desirable to ethnic diversity. Ethnocentrism is the winning survival strategy

https://www.theoccidentalobserver.net/2017/02/24/aristotle-on-immigration-diversity-and-democracy/

Aristotle is greatly concerned with the preservation of civil peace in the city-state. One of the most common causes of “faction” and civil war, he says, was the unhappy consequences of unassimilated immigration and the consequent diversity. Aristotle’s prose is perfectly clear:

>Heterogeneity of stocks may lead to faction – at any rate until they have had time to assimilate. A city cannot be constituted from any chance collection of people, or in any chance period of time. Most of the cities which have admitted settlers, either at the time of their foundation or later, have been troubled by faction. For example, the Achaeans joined with settlers from Troezen in founding Sybaris, but expelled them when their own numbers increased; and this involved their city in a curse. At Thurii the Sybarites quarreled with the other settlers who had joined them in its colonization; they demanded special privileges, on the ground that they were the owners of the territory, and were driven out of the colony. At Byzantium the later settlers were detected in a conspiracy against the original colonists, and were expelled by force; and a similar expulsion befell the exiles from Chios who were admitted to Antissa by the original colonists. At Zancle, on the other hand, the original colonists were themselves expelled by the Samians whom they admitted. At Apollonia, on the Black Sea, factional conflict was caused by the introduction of new settlers; at Syracuse the conferring of civic rights on aliens and mercenaries, at the end of the period of the tyrants, led to sedition and civil war; and at Amphipolis the original citizens, after admitting Chalcidian colonists, were nearly all expelled by the colonists they had admitted. (1303A13)

Thus, immigration of different peoples was a common source of conflict, often leading to civil war and concluding with the ethnic cleansing of either the native peoples or the invaders.

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Ethnic diversity doesn't result in greater unity, it brings the opposite, and it's precisely why it's been sold to us as desirable