Many people erroneously feel justified in ridiculing a Torah lecture or sermon.  Unfortunately, this practice is quite common and the source of serious harm.  Even if it is true that the delivery was poor or that the content was lacking depth, you are prohibited from mocking or ridiculing the speaker.  Your assessment of the lecture is in many instances largely subjective matter.  One person may enjoy light parables, while his friend prefers intricate philosophical discussions.  Even though you did not appreciate what was said, others might have.  In any event, never belittle the lecturer.  ~ Guard Your Tongue