Dear LIB readers: is it proper to answer sir to your husband?

From a LIB reader:

My colleague does this and when I advised her to stop it, she took offense and stopped talking to me. She said we modern women have no respect any longer, that her mum called her father sir and told her it was the respectful thing to do. Whenever her husband calls her on the phone, she answers sir. Is that respect or fear?

I think calling your husband sir is ridiculous! Your boss and an older person, definitely, but not your spouse.