...The way I saw it, I had two options.
Option A: "You don't say! Ma'am, I am so sorry. We'll have our Library Gestapo place a pink triangle on the cover immediately."
Option B: "Um...okay."
I was very seriously afraid that the sarcasm of Option A would escape her, and I hated the meek acceptance of Option B, so I just said, "Oh, thanks!" and immediately checked it out to myself.
Context enjoys gay soldiers.