I focus on an absolutely fundamental difference between cultures on the matter of gender relations, yes, not on superficial differences.  I have yet to hear anyone deal with the issue rather than simply brushing it away with that kind of "oh, racism!"

Yes, I consider it a fundamental difference in how cultures conceive of how a society should be structured, and it is incompatible with ours.  In small numbers, in marginal groups like the Hasidim, it isn't a major problem, but it is in Europe when large groups start demanding that in a multicultural society, they can not only live in their own parallel universe according to those principles, but also want to make others "accommodate" institutions to them.

I welcome those Muslims who want to immigrate here to escape those fundamentalists in their own country, but not those who want to reproduce that way of life here, as multiculturalism encourages them to do.