It seems to me that offense at such questions being asked back is itself an indication of a misunderstanding of the meaning of the word "interview". The "inter-" part of the word denotes mutuality or reciprocity[1], that the questions and answers go both ways, so both parties may learn more about each other. An interview is not supposed to be solely an inquisition wherein the potential employer evaluates the applicants worthiness of the privilege of employment. It's supposed to be an exchange wherein both evaluate if this is a mutually beneficial business deal. And if a company considers it rude for you to want it to be anything other than a one-way inquisition of you, I think that's an indicator that management culture at that company will make for a work environment that's more stressful and less fulfilling than the rose-tinted one they present in the interview.
An aside, I say the above now, but damn, I wish I'd had understood it 10 years ago.