Now, that is a bit surprising as an answer to me. But the reason I am having this discussion is to get new facts from other people about the subject and new facts are often surprising, so this is good. Can you elaborate a bit on the "isolated from the rest of society" part? I'll give my answers later.
First let me state that rational or logic behind irreconcilable disrespect is never a
sine qua non of group self/public isolation.
When I was privileged as a teen in the U.K. To pass the 11+ examinations and gain entrance to a fine richly academic grammar school, I was assigned to the “House of Ellis” , and green Rugby football jerseys as opposed to “House of “Radcliffe” with, (if I remember correctly), purple or the other several color-coded divisions by “Houses”.
That assigned color, turned out, governed much of our attitudes and relationships with others. Those of the house of Ellis bathed naked together after a game in a very long 20 to 30 ft bathtub to get rid of the mud of the rugby field.
We were bonded and had disdain towards anyone “Radcliffe”. We didn’t need to think about it. Radcliffe boys were obviously always arrogant and we were, equally “obviously”, better!
So, here, the trigger for self-sustaining, (mutually opposed), competitive groupings was that irreconcilable difference in color of uniform. It would be absurd for me to try to fit in as a Radcliffe pupil by wearing one of their sweaters!
So it seems that there has to be merely a discoverable difference to recognize and isolate “foreigners”. In Christian Europe, other schoolboys might pull down a boys pants to discover a circumcised Jew, and dishonest privileged Christ-killer), as otherwise many Ashkenazi’s look as Caucasian as Poles and Slavs.
[BTW, for years I went to primary school in London, under police escort!]
Segregation of blacks is easier, unless the lights are off.
For segregating anti-vaxers, simply ask for a vaccination certificate for entry to public events, restaurants or wedding parties!
The party having the power and authority to decide “who is allowed in” gets to feel righteously powerful and the offended, righteous victimhood!
Asher