Where does the article make the suggestion that he was muttering the words 'bomb' and/or 'terrorism?' Even then, why would someone be walking through an airport saying "bomb" or "terrorism" disjoint from any sort of context? (And how does that necessarily make them any more or less dangerous than anyone else? When was the last time that an actual terrorist was caught because they said, "bomb," and someone tackled them?)
As to trying to memorize the words, yes that is the point of Arabic-English flashcards, but how does one become dangerous (or a terrorist) because they are trying to memorize the words "bomb" or "terrorist?" Am I now dangerous because I've just admitting to knowing both of those words (by virtue of using them in this comment)?