hi dig,
on this, i don't really have a good solution. one wishes integration is possible. but it sure doesn't occur quickly.
there are clearly some benefits to a mixed culture society. but we tend to pretend when we look at the costs side of the ledger.
i've talked a bit about core secular values that have to be the foundation of a functional society. these include notions like a person gets to be free in certain ways such as religious choices, that no one is above the law and that the law evolves over time.
i don't see how we absorb beliefs which are contrary to that foundation. folks who want to impose god-given law and who seek to harm those who change their mind about their beliefs are not going to absorb unless their own beliefs reform.