Dickens puts it exactly.
it is a power imbalance.
the woman is at work, carrying out a role, that involves serving customers.
she has to be polite, so has to tolerate some irrelevant comments.
but where is the line.
i don't think she was rude in this scenario.
it's not like at a party or meeting where everyone is in the same category, and can turn on their heel, or be dismissive of impertinent comments if they wish.
when i was working i needed the cooperation of a person who was also in public service.
it was a simple matter, i and a colleague visited her at her workplace and she completed the paperwork.
before she had signed it, she made a remark based on a racist assumption re one of our surnames.
i was taken aback by a professional educated person, a dentist working for the RAF, making such a comment about another public servant.
but i didn't feel i could say anything, as we were focussed on the investigation.
her statement was a small part in a chain re continuity of evidence.
she had no objection to "helping us with our enquiries"; as often occurred, she found it a welcome change to her usual workday.
the comment showed her underlying racism, and probably would have been made in any context.
but from our point of view, we didn't feel we could challenge it.
we concentrated on remaining professional.
and i still remember it decades later, and feel i should have said something.