Lesson 1
When someone asks you a question, s/he is making themselves vulnerable. They are admitting that they don’t know something. Some people feel so awkward about asking questions that they avoid it at all costs. Its important to be sensitive to the questioners feelings. Saying things like "that was a stupid question..." violates the Torah command not to inflict pain with words. This will intimidate the person and prevent them from asking for vital info in the future.
Lesson 2
It is considered avak lashon hora (a tinge of lashon hora) to praise a person in the presence of people who dislike them. This praise can provoke the listener to speak lashon hora. Even if the statement doesn’t contain praise, you shouldn’t even mention a persons name in the presence of those who dislike them.