In the wake of the Christmas Day attempt at man-bombing a plane, there has been a renewed level of agitation from the right-wingnuts for racial and religious profiling to be used for screening people at the airport.
The problems with this are myriad. How do you identify someone's religion? For that matter, how do you identify if someone is of a particular ancestry - especially in North America where there are a lot of people born and raised here who might appear to be of Arab ancestry? Or for that matter, just what makes someone "visible" as a member of a particular ethnic population?
The practical answer is that you can't - and it won't work - ever.
Such approaches to threat management are just as ineffective as the ridiculous restrictions that have been placed on people flying into the US in the last week.
They do, however, have some insidious side effects that we should be thinking about. Let us presume, for a moment, that there was such a profiling scheme implemented. In effect, what you have just created is two queues at the airport - one for whatever group(s) you designate as deserving additionally scrutiny, and one for the rest of the population.
How is this any different from the racial segregation policies that were a part of South Africa's Apartheid era?
They aren't. Period.
In fact, such policies plant the seeds for the same kind of insane limitations on freedoms and liberties that were in place for decades in South Africa. (Not to mention segregation era USA, come to that) What they do is confirm the assumed notion that so many people have that being different is somehow a threat. This is precisely the kind of policy that makes neo-Nazi and other racist organizations ecstatically happy - because it gives them the "moral authority" (in their view) to beat the tar out of whomever raises their ire.
In fact, what it lays down is the foundation for exactly the kind of racism and bigotry that our very laws have been designed to eradicate.
As an aside, just how do you "know" somebody's religion? You can ask them, but the determined will quite happily lie to you about it; and people change religious affiliation all the time. How many of us in this society are "lapsed Catholics", or perhaps are Catholics that switched to one of the Charismatic churches?
The real answer is to investigate and root out threats one at a time - as they turn up. Not with heavy military action, but with counter-intelligence and espionage. Focus on undermining the very organizations that facilitate these actions the same way they operate - in the shadows.