I've really bitten my tongue not to respond in this thread... but manners and etiquette are about mutual and self respect. Acting dignified with self respect is a gift a man gives himself, that others cannot take. If you -
stand for the pledge of allegiance
say please and thank you
et.al. you are involving yourself in the public system of etiquette. Wearing appropriate attire shows pride and respect to others in whose company you find yourself. If you can't be bothered to comport yourself with care and minimal effort, it speaks volumes to others about your character.
Going to church naked doesn't "hurt" anyone, and I hope that shows the ridiculous backwardness of that line of thinking... words like class, dignity, gentleman, etc. all indicate a familiarity with carrying oneself in public in a dignified manner. Walking into a nice restaurant with a ballcap and flip-flops shows those words are unfamiliar to the wearer...