2/3
Lost in the dust up over the executive order are several important facts:
Persons applying to come to the United States are already subject to careful scrutiny. It takes at least two years to complete the process. Trump has never articulated what he means by “extreme vetting” and has never indicated what he would do differently from what is being done now.  I don’t think anyone believes that he has any plan beyond blocking Muslims.  No-one from any of the countries he has targeted has ever committed an act of terror in the United States; the countries from which terrorists have in fact come to the United States are not on the list.
The president has broad authority over immigration policy, and Trump may eventually win in court -- but only if he can sustain the fiction that he is not attempting to ban Muslims qua Muslims.