Simply point out to them that there's a part of the world where Islam is dominant, and there's another part of the world where Islam is not dominant. If they want to be Moslems, go to those places. Otherwise, until they are sufficiently assimilated they have to attend Lutheran services at 7:30 AM and Catholic services at 9:00 AM on Sundays, and try to find a Baptist or other Protestant service for Wednesday evenings. Else they can just go home!
We in the US really ought to demand for a start, all sermons in the mosques now be delivered in English.
The Germans have started to demand German language sermons in their mosques.
We have to know what is being said.