Even if profiling could detect every terrorist, it could not detect every terrorist plot. Remember Pan Am Flight 103, which blew up over Lockerbie, Scotland? That was accomplished without any terrorists aboard. An unsuspecting passenger was turned into a weapon of mass destruction when she carried on a bomb disguised as a radio. Profiling would not have stopped that plot.
[From an article in The Philadelphia Inquirer supporting the enhanced passenger screening procedures for anyone boarding a plane in America by Louis Lombardi, an attorney and former New York City police captain.]