Rav Avigdor Miller on Leitzanus in the Beis Medrash
Q: Why is it that in some yeshivos, and in some batei midrashim, there is sometimes an atmosphere of sarcasm and leitzanus? Is that really a good thing?
A: It depends what they are making leitzanus about. If it’s about evil things, then we’re all for it! That’s what a beis hamedrash is for, to learn how to belittle the evils of the outside world.
But if they’re making leitzanus of good people, let’s say a misnagdishe boy is making fun of chassideshe rebbis, that’s a big error, a big mistake. You have to be careful who you are talking about. And if chassidim make leitzanus about misnagdishe gedolim, that’s also a big error. Those are fatal mistake to make. Nobody should ever make leitzanus about anything unless he knows that it’s absolutely wicked.
Tape # 498 (March 1984)
Letzonis is never good especially when it hurts someone. מלתא דבדוחתא is encouraged to liven the atmosphere,. because mitzvas and learning should be done from joy.
If we pay more careful attention, we will see that the word ליצנות is always used in a negative context, and that it is always אסור, with the exception mentioned in Shas of ליצנותא דעבודה זרה. As mentioned in the above comments, the degrading of evil is a positive thing. Anything else is a bad midoh. We are instructed many times to avoid it.
In contrast, the gemora extols the virtues of מילתא דבדיחותא, with references to being an appetizer for learning, and creating שמחה. There are פסוקים to the effect of כל השומע יצחק לי and the like that are quited to support the virtue of being in a happy mood and laughing. The laugh at the expense of another is ליצנות, and it is a pretty awful thing.
To be specific about the question of the heading on this thread, ליצנות is always bad, except for ליצנותא דעבודה זרה (and whatever is included in that). בדיחה is a positive virtue.
The Little I Know, see what I said on the topic of hachocho in the name of the Shlah Hakodash about a letz.