It is not entirely clear that Khazir Khan’s son having been born in, the UAE wouldn’t have been able to move to the US as he did.
"Mr. Trump’s policy director, Stephen Miller, said in an interview with The Wall Street Journal on Monday, “The best way to prevent continued radicalization from developing inside America is to suspend temporarily immigration from regions that have been a major source for terrorists and their supporters coming to the U.S.”
wsj.com/articles/donald-trump-back-pedals-on-banning-muslims-from-u-s-1467058774
Would the UAE be one of those countries under that suspension? I don’t know.
You are saying it is unconstitutional, but there are differing views. I’m not sure there has ever been a test case that has went through the US court system to say for definite, but it is not clear that it is unconstitutional.
I’m not saying the idea of a religious test is a good idea, but the point can be made that Trump’s Muslim ban can be seen as a response to terrroism and if the Obama administration and other governments had managed to deal with the threat of terrorism in a better way, would we be even discussing such a proposed ban?