No, I can't just forget ethnicity, because this is moving the goalposts.

Maintaining a 'culture" is largely meaningless. What is America's "culture" for example. What steps do you take to maintain it? If you're talking about laws, like sharia law, then we can talk meaningfully about whether those laws are just or not. Just as, 80 years ago, we could have talked about whether segregation or Jim Crow was just or not.

This is obviously very different to maintaining a certain ethnicity as the majority. Again, this latter fundamentally requires racism and ethnic cleansing.