It's amazing that Catholics who have no objection with race mixing....
The Church Herself has no objection to it.
What God has joined together...
Please show Church teaching, doctrine or dogma against racial separation or forced integration or ethnic/racial groups freedom of association within their own subsect.
I'll be waiting.
Er, no.
You have to show that the Church supports, nay demands, racial separatism, and opposes miscegenation.
She does not. If She did, you would be able to find some magisterial teaching condemning racial mixing and demanding separation.
No such teaching exists.
However, the Church's practice (and not just post VII) demonstrates that She does not forbid races mixing, socially or matrimonially.
What God has joined together... as I said above.