I don't know what exactly they claim, but I have a hard time believing that they actually believe Blacks/Hispanics/Jews...... are equal to whites but they just shouldn't mix.  That may be a line they say, but it doesn't pass the sniff test.  If a white person doesn't want to live with anyone but white people, it seems to reason they might think of themselves as superior. Just a hunch.
I think there are so many problems, but you have certainly laid out one reason why it would never be functionally possible. I suppose, "white separatists" could seclude themselves in some small community, as I'm sure many do, but not societally.  Thank god.