Not too long ago, I was working in a supermarket in the Deli department. There was a customer that came in on a regular basis, a grumpy, older person. I was always nice to them and treated them the same as everyone else. The thing was, they were wearing woman's clothing, though I could tell they were, at least born, as a man. I didn't quite know how to address them, so I never used any gender specific pronouns while serving them.
The problem happened a few weeks ago when I went to the store as a man [or at least trying my best, since I can only sometimes pass as one]. I happened to bump into my former customer, and said "Oh! Excuse me, ma'am!" to be polite. They immediately got angry and yelled "I'm a MAN, don't call me ma'am!" I was a bit flustered and embarrassed at the whole thing, and quickly left the store. I feel bad, but I really don't know how to deal with that sort of situation.
I guess my question is, what would you guys do in that sort of situation? He was wearing a skirt, had breasts, lipstick, earrings, feminine haircut and everything, and when I didn't know him personally enough to ask what he preferred to be called. And when I worked at the store, he was in there every morning, and never once dressed like a guy. I said "ma'am" because I had more than half expected him to say "I'm a WOMAN, don't call me sir!" if I had said "sir".
