"Nobody from those countries has committed terrorism!" Wrong.

Last year the Senate Judiciary Subcommittee on Immigration and the National Interest released information showing that at least 60 people born in the seven countries had been convicted — not just arrested, but convicted — of terror-related offenses in the United States since Sept. 11, 2001. And that number did not include more recent cases like Abdul Artan, a Somali refugee who wounded 11 people during a machete attack on the campus of Ohio State University last November.
So the argument will now become "Only a FEW people from those countries, so it's not worth troubling over!" 

Guarantee it.