Every nation should aspire to generate conditions of tolerance in which ethnic or racial differences don't represent a threat to the safety of their communities. However, this is a long and arduous process that involves many factors and may require several centuries in some cases.
Sometimes the tensions between different ethnicities and cultural backgrounds are so high at certain moments in history, that there's no other way to ensure safety than limiting specific types of immigration in regions that may will be hostile to them. That is why to me, it is legitimate for a country to take nationality, race and religion into account when deciding who they let in, as long as the government keeps moving towards tolerance in the long-run.
Hope this helps!
