If one were to conduct an exit poll at the conclusion of a lecture, he might possibly hear dozens of varying opinions on how well the lecturer spoke. While many of the opinions might be positive, there is a likely chance that at least some would be negative. Criticisms might range from “He doesn’t delve into the subject matter enough,” to “It was so deep, I got lost.”
The Chofetz Chaim teaches us that when leaving a lecture, especially a Torah lecture, there is something we need to realize. Each person judges from his own vantage point. To people who are very knowledgeable, the lecture may not have been deep enough, while to those who lack that depth of knowledge, the lecture might have been too complex. Opinions in such matters are usually subjective. For every complainant about a lecture, there are many people who want exactly that type of delivery. The fact that someone did not enjoy it does not mean that it was not good: it means that the lecture did not suit his particular taste.
The Chofetz Chaim goes to great lengths to emphasize this because many people have the habit of criticizing lectures, unwittingly causing much damage to the lecturer’s reputation.
The halachah identifies a particular nature of the human psyche. We can express it as follows: If I have listened to a lecture and my friend denigrates it, then even if I enjoyed it, I will subsequently think less of the lecture and by extension, the speaker as well. Although at first dissatisfaction with the lecture was only my friend’s feeling, after he shares it with me, it will influence my opinion as well.
That people are entitled to their opinion is a principle held with near-religious fervor in any democracy. The Chofetz Chaim is not telling us that we should not have our own opinions or that we must enjoy every lecture we hear. What he is saying is that we are not allowed to verbalize our negative opinions without a constructive purpose.