Was this inadequate behaviour due to poor situation awareness
No. It was just piss poor attitude and is a generational thing based upon general contempt for authority. The military pull those types into line quick smart but airline managements avoid the issue and pretend it does not exist on their flight decks. The first officer could just as easily have said no problem and turned to the new heading as politely requested by the aircraft captain. There was no loss of face or dignity. It was just a heading change, for Christ's sake. Instead he chose to be a smart-arse.
