There can be no doubt that Captain Kahn was a hero. But the fact of the matter is that less than 1 percent of U.S. personnel killed in the Iraq/Afghanistan conflicts were Muslim. I imagine there were some Wiccans, and maybe an atheist or two. Trump's idea to ban all Muslim immigration is likely unconstitutional and undoable. But more careful vetting of immigrants from trouble spots may certainly prevent the disaster that is happening in Europe now. Immigration quotas and requirements are nothing new; those laws impacted lots of our forbears back on Ellis island. Look up the Johnson-Reed Act.