You dont know how many times I have said, “Blame my mother”, after upsetting some lady by calling her “ma’am”.
If she was upset, she wasn't a lady.
The reason some ladies get offended by “ma’am” is because for one thing, it makes them feel old. When you’re in your teens or twenties, you’re called “miss,” then all of a sudden, you start hearing “ma’am” instead, and it makes you feel ancient. Also, some employees are taught to call all female customers “ma’am,” but they do it in a very snotty, impatient way. Like a female comedian I once heard says, “We all know what ‘ma’am’ means when a department store saleslady says it. It means the ‘B’ word!” :-)
But of course none of this is your fault. It must be annoying to behave as a gentleman, only to have women respond by getting offended. I hope it helps somewhat to know where those women might be coming from.