“I think it is more than reasonable for a shul to have a fair reason for having a rule requiring the baal tefila to wear a white shirt on Shabbos.”
every locale is different. what is “respectable and accepted” in one place is not in another. ever see how an executive in brazil goes around in the summer? a jacket is already two steps up. in a place where a white button down shirt is standard weekday fare of course something more is expected on shabbos, or even for shul.