After a flight? What is the point of searching them AFTER a flight?
Well, it was after a commuter train ride, but your point is well taken. I'll tell you what their point was: they attempted it because they felt like it. Thank God for the local Amtrak Police Chief to told them to take a hike.
You've got an out-of-control government agency with power, you've got thousands of mall rent-a-cops with guns and barely high-school education levels, and a burning desire to justify their existence - it's a toxic mix that's not good for anyone.