It's all window dressing, if you wanted to create carnage, you could just nip down to the Trafford centre where you'd have 10s of thousands of targets. No metal detactors there.
And yes some security staff are proper brainless w@nkers, one particular favourite was being stopped on Christmas Eve in BFS. Now I'd commited the heanous crime of collecting a wrapped present from my ex-partners parents, was then asked "What's in it?" and forced to open it, even though I had to point out the Rapiscan showed no organic material in it. Totally brainless.
As much abuse as the TSA get, I've always found them to be friendly and courteous. Some UK one's have some bizarre megalomaniacal complex.