Why don’t we only search terrorists?

Bruce Schneier answers the question “why do we bother making people with security clearances go through airport security?” with the obvious answer “how would an airport screener know if you have a security clearance?”

Heck, as long as we’re living in fantasy land, why don’t they let non-terrorists bypass security and just focus on The Terrorists? After all, it must not be too hard to tell who’s a Terrorist and who isn’t, since we’re already single them out for torture, rendition to Syria and indefinite detention without review. What’s forcing them to spend extra time in line at the airport compared to that?