Hi Capt, I just want to say that as a person who works in the public 6 days a week, I'm a cashier at a restaurant, sometimes I will say ma'am to a genetic male, and sometimes I will say sir to a genetic female. In my defense, it is simply that I am overly tired or extremely busy,ie; 23 women followed by a guy and I accidently say ma'am. However, I ALWAYS correct myself and apologize. The thing is we live in a day and age where some people don't care if they make a mistake or are just plain rude. I'm not making excuses for anyone but sometimes you have to give the benifit of doubt, or just ignore the insolent behaviors.
If someone insists on continueing to call you ma'am, or they question you after you have corrected them [in a nice and respectful manner] then take it up a level and ask to speak to the manager. No one has a right to be openly rude and disrespectful esspecially in a service oriented business. ie; sales clerk, cashier, bank teller, etc. I hope this helps in some small way.
Take care and good luck.
CG gg