Nobody's suggesting that it should be a crime to trigger a metal detector whilst trying to board a flight with a checklist of words related to terrorism in one pocket and a book apparently accusing the US of being a "Rogue Nation" as further light reading material. They are suggesting it might be a sufficiently unusual set of circumstances to warrant waiting for a competent investigator to give the all clear.
As entirely explicable as his actions might have been, this guy did an awful lot more to inadvertently provoke suspicion than the several people per day detained for questioning for being in a particular area at a particular time, and possibly even the same colour as the perpetrator. A few of them undoubtedly suffer the inconvenience of missed flights and public embarrassment too, and/or encounter more objectionable behaviour from law enforcement than a overuse of handcuffs and amateurish-sounding line of questioning.
The actions of the police bear explaining, however, regardless of how suspicious they though the actions of the traveler were. IANAL, but as I understand it, if police handcuff him, he was being arrested, which means the police failed to read him his Miranda Rights and to charge him with any crime. If this is so, isn't that either a crime on the part of the police themselves or at the very least a serious administrative violation? The alternative is that he was being detained for questioning, but is it really usual or accepted to detain someone for a long a period of time and handcuff them for questioning? (seems 20 minutes is considered already fairly long for this sort of detention: http://criminal-law.freeadvice.com/criminal-law/arrests_and_... , though I can't verify the source ). The question here is under which law or authority can someone be hand-cuffed and deprived of their freedom - however briefly - just for having a bunch of cards with words and a book.
I mean, I am not kidding myself, the "threat of terrorism" has been used to justify far worse abuses, up to and including torture and extra-judicial prisons. But expected or not, this should be morally and legally indefensible.
Also, at a personal level, it makes me think that, should I decide to travel any time soon, my reference papers for work in computer systems' security, the book I am reading on the NSA/Snowden material and my textbook on introductory Chinese should all stay back home. Because "that sure looks like some suspicious literature right there, doesn't it?"
As entirely explicable as his actions might have been, this guy did an awful lot more to inadvertently provoke suspicion than the several people per day detained for questioning for being in a particular area at a particular time, and possibly even the same colour as the perpetrator. A few of them undoubtedly suffer the inconvenience of missed flights and public embarrassment too, and/or encounter more objectionable behaviour from law enforcement than a overuse of handcuffs and amateurish-sounding line of questioning.