I don't think his point was that he was upset for them not holding the flight up (although it probably wouldn't have killed the gate agents to do so considering he had them page his daughter and they knew he was going to get and come right back). After all, SGB dictates that a rule is a rule.
Rather, I think he was pointing out the lack of professionalism that these two gate agents exhibited. Truthfully, I would be livid if someone treated me that way too. I would expect them to treat all passengers, especially Medallions, with kindness and respect.
Yes, Peter King can exaggerate from time to time but avid readers of his MMQB column (of which i admittedly am one) also find him to be truthful and respectful of others. My guess is that is all he wanted in return.