There were a number of terrorist incidents committed by Muslim refugees and their second generation offspring  in the United States over the past year alone, e.g. the Somalian refugee who ran down and stabbed randomly students at Ohio State University back in late November; the refugee who went on a stabbing rampage in the mall in Minnesota; the pipe bomb in New Jersey that targeted a U.S. Marine Corp charity race; as well as an incident involving a country not on the list, i.e. the second-generation son of an Afghan immigrant who butchered 49 people in Orlando, etc. The reality of an ever-increasing number of terrorist atrocities or thwarted attacks perpetrated on American soil by Muslim refugees, immigrants or their children should be quite evident and concerning to anyone who bothered to do a simple news search. I doubt many on this page would be so blase about the threat were it one of their family members who was killed.