Firstly, he was obviously scanned and wanded in the airport where he was wearing these things openly.
Secondly, this country was founded on freedom of religion and should be protected from hysterical ignorance (not on your part but the pilot/crew).
Well, the TSA does not exactly have a sterling reputation for screening out potential terrorists and their carry on equipment.
It is understandable how flight crews would be nervous these days, given the events of the recent past.