Because he's always stopped.
We're still talking about the Jewish guy, right? How often does he fly, anyway? What's the sample size?
Please do let me know because this "disproportionate" response to 9/11 against Arab/Muslims (i.e. wanding your Jewish friend at the airport) sounds very scary indeed and I want to quantify just how terrified I should be!
Sorry, it's just that I'm finding myself utterly unable to take you even remotely seriously any longer.
"Because he's always stopped."
Only a complete idiot would mistake an Orthodox Jew in Orthodox garb as being an Arab. But then, some of these screeners aren't the brightest bulb on the tree. At the same time, being dressed as an Orthodox Jew would be the perfect cover for an Arab terrorist trying to give airport security the slip, so I don't blame them for checking him.