Cops have dogs trained to give false positives on signal and we are constantly spied on and lied to by our own intelligence agencies.
So please don't tell me this idea is far fetched, I think it's very plausible.
It would be damn hard to prove the last, but what is relatively easy to demonstrate is that dogs do give false signals that correspond to certain biases of the owners. Regardless of whether the last is true or not, the way we view detector dogs needs to be revisited in light of these clear biases. As it is, detector dogs seem to be barely better than dosing rods.
When working security, agents can sense something is wrong but not have it articulable enough in legal terms to act on. When the suspect says "why are you searching me?" it's a lot easier on everyone to say "the detector beeped, you heard it" than "I've got an uneasy feeling about you". (Not legal, not warranted, just easier.)
The only reason to keep screening him over and over is if the detector really did find something, otherwise they are just wasting their own time because of a nebulous feeling.
Why make this person crack.
I've never been in the US, but when I travel (Europe, MENA), I am always chosen by airport security, even in my own country when leaving, for an additional search (less annoying than a TSA patdown I read of, but still), and when I asked recently why is it always me, a guy answered I was randomly selected by the gate. Got to start buying lottery tickets.
Indeed, the narrative of this very story seemed to be overwhelmingly focused on figuring out why he was setting off the explosives detectors. They repeatedly went through his belongings and tried to figure out if he was indeed in the business of making explosions. They almost certainly used a secret warrant to go into his apartment to, again, see if there was an explosives lab there. They really thought they had something when the explosives detector found something it didn't like, and there is no rational reason they would do this just because someone was Muslim (again, Muslims make hundreds of millions of flights in the US -- do people seriously think this is what they go through?)
The only way to keep a secret for long periods is that few know about it.
Not that I believe that there's a secret button.
Interestingly enough, most classified information doesn't get leaked the same way that Snowden leaked his documents. It's mostly due to carelessness. The best example of this is deployment schedules. One of my coworkers was scheduled to go on a Marine Expeditionary Unit (ship that goes around the Pacific just in case something happens). The date of departure was classified. Someone told his wife, who told all of her friends on Facebook. Oops.
Trying to keep a "detain"-button secret, having it manned by thousands of people that only have a high school diploma OR a year of work experience in security/aviation/screening, doesn't sound easy (those are by the way the education requirements for a TSO according to usajobs.gov). Since a leak could stem from a minor overstep of their contract (ohh, I told a buddy about it, big deal right?), and there are frequent policy violations by agents, it does look grim for the existence of such a button.
I heard of them kicking the machines to make them go off though, so there's a "button", and it's public knowledge that they will use it if they want a pat down.
That exact thought crossed my mind afterwards.
In the end, they never showed me any evidence that the machine had actually detected any explosive. Nor did they figure out what could have caused the "false positive".
Maybe they did detect something, but then what's equally surprising is the thought that they would then just let someone go after they have walked into JFK with explosives on their body.
What does the TSA agent get out of needlessly fucking with some random person?
Also I can imagine a number of rationalizations and psychological mechanisms that can explain how working for this kind of organization affects people - the Stanford Prison Experiment etc.
http://www.smbc-comics.com/?id=3025
Not that I don't broadly agree.
I remember that when I was reading Zimbardo's book I was most touched when he was describing how he himself was under the influence of the experiment and his empathy to "subjects" deteriorated. Only after his girlfriend expressed her concerns he realized that something went horribly wrong. We are influenced by the context, behaviour of others, interpretation of the situation etc. way more than we would like to believe and I can easily imagine that if I were one of those TSA agents I could behave in a way that I now find despicable. That's why I think we really need to be aware of those things despite the fact that they might not be conclusively proven as a 'part of human nature'.
EDIT: also let me mention another IMO super-interesting book about this subject: The Anatomy of Human Destructiveness by Erich Fromm. One of the best books I've ever red.