This is really difficult to say.... Ummm.... In this matter I really AGREE with BobF!!!! There, I've said it!!! Hope I don't have to again!! :>)
American has a long history of accepting immigrants from across the World. My goodness. Irish, German, Asian... the list is long as to how we have been a melting pot of nationalities, races, AND religions. Those who have immigrated have become our business owners, craftspeople, chefs, teachers, leaders. This is who we are as the United States!!!
Today, we have a predominate sect of a major world religion that has sworn to kill Americans. This group of numbers in the tens of thousands and is one of the fastest growing in the world. They are preaching that everyone who does not believe as they should be killed. There is no tolerance of other religions... Christian, Jew, Hindu, etc. In fact, there is no tolerance for fellow Muslims who do not hold the same convoluted view of Islam as to they. The radicalized Muslims have raped, beheaded, shot, burned more of their fellow Muslims than of any other religion.
The terrorist groups have told us they will murder Americans in our own cities exactly as they have done in Paris. They have told us they will infiltrate the refugee streams and use that as access to our neighborhoods. There is no means of "sorting" out the bad from the good. Two fellow Muslims can be questioned and give the same identical answers that they are peace loving and not radicalized. How do you "prove" that they are both telling the truth. One may be. Both may be. Neither may be. Most of those who have struck terror across the world are not fingerprinted and don't have a history of lawlessness recognized in no-fly lists. Even if they do, false ID is merely a couple hundred dollars. Today, 5 Syrians were arrested in a neighboring nation attempting to enter the U.S. with forged passports. At this point in time, I don't want our schools, universities, athletic stadiums, shopping malls blown up by the one or twenty who make their way through the system as refugees.
Paris was one wakeup call. The Russian passenger plane another. The entire world is beginning to sit up and take notice. I feel as more and more countries realize they must join the fight and wipe out this cancer before it wipes the rest of us from the Earth, we will win. The fight will be difficult because it's not "trench warfare". We will continue to see terrorist events take innocent lives just as in Paris this past week before this is over. Until it is over and until we can find some means of knowing who is... or can be... radicalized we must first think of our own families, neighbors, citizens. I know that sounds cruel and heartless. I'm not!!! This is a very specific and very dangerous problem!!!