If 85 percent of group A are fine people and 95 percent of group B are fine people, that means you are going to be importing three times as many undesirables when you let in people from Group A.
Citizen-of-the-world types are resistant to the idea of tightening our borders, and especially resistant to the idea of making a distinction between people from different countries. But the real problem is not their self-righteous fetishes but the fact that they have intimidated so many other people into silence.
In the current climate of political correctness it is taboo even to mention facts that go against the rosy picture of immigrants -- for example, the fact that Russia and Nigeria are always listed among the most corrupt countries on earth, and that Russian and Nigerian immigrants in the United States have already established patterns of crime well known to law enforcement but kept from the public by the mainstream media.
Self-preservation used to be called the first law of nature. But today self-preservation has been superseded by a need to preserve the prevailing rhetoric and visions. Immigration is just one of the things we can no longer discuss rationally as a result.