Did not know that, BUT if the reasons given for standing are true, that a monarch stood and customs dictates all his subjects stand, then as an American, It would not be upon me to stand, as an american citizen does not acknowledge a monarch authority over an american citizen and would not follow that ON american soil!!
However, if visiting, a forign country, it is customery, as a courtsey, to follow custom...
All that aside, I think the director needs to have a dose of reality, most programs usually state when to stand, and being rude to the audience is not warrented!