Question:If Huemer is right that the practice of forcibly denying immigrants residence within our borders

Question:
If Huemer is right that the practice of forcibly denying immigrants residence within our borders is not morally justified, then why is it so universally accepted? Does it have to do with, as Huemer suggests, bias and discrimination? Members of a nation tend to see themselves as “better” than members of other nations, and therefore tend to overlook the needs or interests of those others. Just as the racist view that white people are superior led to black people’s interests being ignored, or the sexist view that men are superior led to women’s interests being ignored, perhaps in the same way a nationalist view that Americans are superior leads to foreigner’s interests being ignored. This hypothesis is supported, Huemer says, by the fact that nearly all defenders of immigration restrictions focus on what effect immigration will have on OUR people or OUR economy, with never a mention of what effect it will have on others. 
Do you agree?