Employers should have training for interviewers that includes discussion of protected classes but it's not that hard.
Don't ask questions that are irrelevant to the interview. If you need to make pleasantries, stick to very broad questions, eg "how's your day going so far?", "How about this weather?". There's no legitimate reason most of the protected classes should come up in an interview.
Sometimes people will ask "where are you from?" or similar during an interview, and that's in the off-limits category.
Don't ask questions that are irrelevant to the interview. If you need to make pleasantries, stick to very broad questions, eg "how's your day going so far?", "How about this weather?". There's no legitimate reason most of the protected classes should come up in an interview.
Sometimes people will ask "where are you from?" or similar during an interview, and that's in the off-limits category.