Then you should be able to put on a good show for them. [There's a little bit of actual humor in there along with the heavy sarcasm. He had to make a joke. If he didn't he feels like his own mind might break. Then Vash relents with a sigh.] I'm sorry, Knives. I should have known better. [He had been here months compared to the day Knives had been.] I'll be sure the next time I want to argue with you I'll wait until we're inside. [That's a joke. He's joking.]

Dinner should be ready in probably the next ten or twenty minutes. [Vash sets down their citation down on the table and heads back to the kitchen. Acting like they had simply been discussing the upcoming weather instead of an upcoming lesson in his own personal humiliation.]