To me, this is where the Trumpian approach fails, but also where exclusion of grandparents and grand children really hurts their argument.  The problem they try to address is terrorism.  I agree with dealing with terrorism.  DEAL WITH IT!  Vet each applicant for admission to the US carefully.  Really carefully.  Investigate. 
 Question, Research.  Come up with identifying flags for terrorist tendencies that are objectively real, and check carefully for them.  BUT, don't assume that a person, by accident of birthplace or lineage, is a terrorist.    And, we cannot allow the executive to identify a single repugnant trait in one individual, or a group of individuals, and then PRESUME it as to all who share the same trait.  If so, whomever is in executive power at any given time need only assert a given action by a single individual is a "national security" risk, and then apply it to an entire like nationality, or race, or religion, or gender.  That is the problem with the travel ban.