It strongly depends on the circumstances.
If anyone complained about my ex wife back when I was married to her, I had told them that I didn't care and to go jump off of a cliff. I've given this response to a former colleague at work who complained to me about my ex wife and that he thought she was a "b***h to him. I was married at the time and he was causing problems between me and my ex wife. He was griping about her to me and then going and complaining about me to her. He was stupid.
It was none of his business.
I felt that it was my duty and right as a husband to back her. So I told him off and that I didn't care about his negative opinions about her and that he can't do that. I warned later that I didn't care about his opinions and that he'd get his "ass" kicked if I had any further problems out of him. Thankfully that settled things and we quit talking to each other.