I confess... I am one of those that HATES to be called ma'am. Especially by someone older than me! But it isn't so much about being OFFENDED per se. It just makes me feel OLD! lol! I like the fact that I'm in my early 20s and I wanna enjoy that! I wanna be a miss for as LONG as I can!!!
I do appreciate that a person who calls me ma'am is showing me respect, so I generally don't say anything, but inside, I CRINGE and think "It's MISS, please, if you must use a formality-- I'm younger than you, buddy!" Although, come to think of it, it bothers me more when someone my age or younger calls me ma'am than it does when someone older does...
Anyway, I've heard a lot of people have that reaction, and I think it's more of a "humorous" comment when people say not to call them ma'am and sir, not so much actually being offended. I could be wrong though.
If you were talking to someone like me, and they said not to call them ma'am, I would say for you just to tell them that you were only trying to show them respect. Then they'll feel silly for making such a big deal out of it :P Plus, they will probably feel respected
Angela