If the primary screening was effective and done properly, nobody would need a secondary unless there is an unresolved WTMD alarm or x-ray item. Nobody needs to be profiled, just thoroughly screened. Of course, that means the No-Fly List would be useless. Oh wait, it already is.

If passenger is not in possession of a credible weapon or a viable explosive, it doesn't matter security-wise who he or she is, where they have been or where they are going; or why.

Valid ID - not important. Criminal - not important. Carrying $$$$ - not important. Drugs - not important (although I'll cede calling a LEO in that case).