Isn't the point being missed a little here? With some jobs, a sense of responsibility even when not actually in work is needed - like it or not it goes with the territory. A 15,000 hour pilot with the greatest flying skills in the world would expect to get the book thrown at them if they buzzed Buckingham Palace at 200 feet - the argument that they were no threat (in that case due to their ability to do it safely) would cut no ice. Likewise a police officer, particularly a senior one has a responsibility even when off duty not to ignore laws when they feel like it - or face the consequences. As others have said, saying it once is stupid, but to repeat it, and then to try and initimidate the security guard into backing off by flashing his warrant card is gross professional misconduct in my view.
PS: The point about wanting all pax to carry weapons to tackle hijackers is an interesting one. Presumably this will necessitate 2 channels at each security checkpoint, one marked for ordinary passengers ("is that Uzi part of your anti hijack equipment Sir? Yes - no problem, please proceed"), and one channel for terrorists ("I'm sorry sir, you will have to leave your nail clippers behind"). Hmmm - that could work!!!