Dan Winterland: spot on. It is no justification for illegal conduct, of course, but it matters. Flying today is now a stressful experience for even the calm-headed folk.
I would add that the fact passengers today hardly ever see the Commander (or F/O for that matter) 'in person' thanks to tight turn-arounds / (understandable) rules on FD crew being in the cabin does absolutely nothing to instill respect for the persons of authority legally in charge of their safety and well-being.
AB: not sure I agree with you that the Commamder shouldn't sort out trouble on the ground, if s/he thinks that is appropriate. Again, if we never actually see you...! Would have thought a visit to said passenger (maximising their embarrassment) along lines 'behave or I'll have you escorted off this flight' is a very effective way to fix a problem?