In my mind this is the best advice - the only I would follow. Don't respond to the raving and incensed. Instead let them pursue remedy with the relevant autho

In my mind this is the best advice - the only I would follow. Don't respond to the raving and incensed. Instead let them pursue remedy with the relevant authority. Then state your case to said authority. All will circle back to the original party, and they'll buy the explanation: authority granted not only because they're the established authority but also because they were independently engaged by the original party.