Mr. Simon and I do agree on many points regarding immigration. But I do want to note where I differ.
I do not think it is immoral to deny a group – any group – entrance to your nation. If the sovereign government decides for some reason that this is the best thing for the well-being of its nation and its people, it has a responsibility to them FIRST, above anybody else.
So if I put a big old sign on the gates of Ellis Island that said “Italians need not apply”, because I am afraid that they will, I don’t know, form gangster groups and take control of cities via corrupt politicians or something, I would have no problem with this, because the responsibility of a country is first and foremost to its citizens. If it feels some group is a threat, then I have zero problem banning them from entry; this is true even if they happen to be wrong.
I DO think countries should probably take in applicants on an individual basis with strict criteria. Ideally I would only take Christians in great need who are willing to abide by the laws and customs of the country, and even then possibly not grant citizenship for several generations. Mass immigration I think is virtually uniformly a terrible idea.
Culture and ethnicity matter.