I once took a graduate course in education in which I was the only non-teacher. One day, I disagreed with something said by another student, and her response has always baffled me. She said: "Who are you? You can't question me until you've walked in my shoes." In other words, she felt that I was unqualified to question her, to cast doubt on anything she said. Who was I to say? Well of course her response was nonsense but how so? As a matter of logic or illogic, was her remark an example of an appeal to authority? She certainly felt that she was an authority.

I agree that the student's response was rude. Not knowing the precise topic of your discussion in class, I am unable to say much. But it seems like the student could have done a great deal more to explain the basis for her view, and it seems like a good teacher would have required her to do so. However, an appeal to authority is not always inappropriate. Suppose an art expert tells me that a certain recently discovered painting is by Botticelli. I could ask the art expert to explain the justification for her view. She might reply that the brushstrokes or the treatment of the hair are characteristic of Botticelli's work, and she might even point out to me the similarities between the given painting and others firmly attributed to Botticelli. But suppose I do not perceive those similarities. I just don't see the "characteristic brushstrokes", for instance. It might well be entirely appropriate for the art expert to say, "Well, I've done my best to show you what I see. But it took me years to perfect...