1. Gerda: So you believe that all belief is the product of custom and circumstance (or: childhood buffets, class struggle...). Isn't that position self-limiting? Mustn't you see yourself as reflecting only a single complex of circumstances.
Grobian: Your objection is inapplicable, for it is merely the product of blind forces. Moreover, your childhood buffets were pernicious and regrettable, for they have set you against the truth.
2. Gerda: So you believe that all knowledge comes from God in proportion to our virtue or worth, and that all ignorance, error, and uncertainty come from the Devil in proportion to our vices. May I ask what evidence you have for this remarkable thesis?
Grobian: I pity you infinitely for your sins.
3. Gerda: Doctor Grobian, I am not crazy! I stole the bread because my children were hungry. Why do you assume that every crime is caused by illness?
Grobian: Why do you deny it?
Gerda: I am not playing a game. I really want an answer to my question.
Grobian: Obviously your ego cannot cope with the truth and you display this inadequacy in hostility to your doctor. I will not recommend your release.
4. Gerda: So you believe x, y, and z. But you are mistaken. Consider evidence a, b, and c. What do you say?
Grobian: It's a mystery. If I could understand it, I wouldn't believe it. I can't help it if it's the truth. One day perhaps you'll see the light too.
All of these involve a pernicious, cheating sort of self-insulation from debate that I feel like I've long hazily perceived and have gotten inarticulately worked up about, but which Suber has successfully tracked down and stuck right in the searchlight. Especially case 4, the "if it were explainable, I wouldn't believe it" defense, which I was sad to see not get as much attention as I'd hoped. But cases 1, ("oh, you would say that, you [member of group]!" 2, ("questioning the dogmata of sin is sinful") and 3 ("questioning the definition of crazy is crazy") are all very important, too.
In the end he concludes that this "logical rudeness" is really only an issue of etiquette, upon which the rules of logic itself must remain silent. Kind of a disappointing conclusion, but I can't come up with any refutation at the moment.