Logical rudeness

Consider the following exchanges:

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 this 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.

In each of these cases something has gone wrong with the process of debate.

Peter Suber, Logical Rudeness, 1987