It seems the main thrust of conservative arguments for banning refugees is that some of them might be violent and it would be impossible to vet all of them. Given that the United States is the most violent nation in the developed world (we have more per-capita murders than any other developed country), then it seems entirely logical that those nations should close their borders to us.
Want to vacation in Greece? Sorry, you might build a makeshift gun and shoot someone.
Want to do business in Japan? How could they possibly be 100% certain that you’re not a violent psychopath?
Build a wall on the border of Mexico? The Canadians should be building a wall on the border with us. Why risk the chance of a violent death when every Canadian life is sacred and no policy is too radical to protect it?