The best thing this guy can do is "own it". I'd suggest he make a poster-sized copy of that billboard and hang it over his desk, rack, or whatever. Then make a bunch of 8x10 copies, autograph them, and hand them out to his fellow officers. He should take all his squadronmate's good-natured jabs in stride and dare them for more. The humor in this event will be exhausted soon enough. In the end he will have shown his toughness, sense of humor, earned some respect from his peers, and ideally tightened up comraderie in the ready room.
At least it used to work like that.
At least it used to work like that.