I noticed with surprise that the NYT article made no mention of the fact that a law enforcement officer concurred with the TSA staff about the key. (OP wasn't clear on this, was it a Dallas Police officer or some other person?)

I think that is a point of concern that really needs to be brought out, since many here feel that involving an LEO is a 'last line of defense' if one perceives unreasonable behavior or demands by TSA staff, but here's a case where doing so didn't help at all.