Well, I hate to say it, but you are right.

It reminds me of a scene in the movie "Spaceballs." The ship is about to blow up, and somebody yells to the president "Do something." He picks up the microphone and yells over the entire ship "Do something."

The people in charge just want to "do something" so that they can say that they tried. Never mind if much thought went into the action, or if anything will even be accomplished.

And even if the random bag searches DID work, then the bad guys would just switch targets. I have never been to NYC or London, but from what I have seen on TV, you just have to send a bomber in the middle of a crowd crossing the street at rush hour. Or, you could hit a mall... or the line of people waiting to get into a popular bar...