And then it hit me.
I probably shouldn't.
So let's just say, I had a student who tried to challenge me. I gave a perfectly reasonable response. She tried again, and the response that came to mind was, "Because I'm not being graded."
I managed to not actually say that to her. However in class today I had a student ask a question about the topic for the paper (not challenging, just asking), and what came tumbling out of my mouth was, "Because I said so."
You win some, you lose some?