If you're teaching youth, you know that on occasion, students will ask disruptive or off-topic questions. I am always trying to encourage my students to ask questions, and I am always worried that shooting down a question too hard will frighten off others who have questions. I have made the mistake before of shooting down a question that I felt was off topic only to realize later it was a genuine question. I felt horrible.
Now when I am asked a question that is a little off, I say, "Ok, let's talk about that. What do you all think?" and I redirect the question to the other students in the class. Suddenly, peers are put in the position of experts, and they respond accordingly. If the student was trying to throw me off, they don't get what they wanted (a flustered teacher), and suddenly their peers are telling them why their question was ill-formed, or they are answering the question like it is valuable. I have found that this peer redirection shuts most question-related problems down almost instantly. If it was actually a serious question, no one's feeling are hurt, because the question has been treated respectfully, and other students had the chance to respond.
I have found that responding to all questions as if they were fantastic, well-though out questions has really improved the culture of my classroom. It is more important to me that I create a classroom culture where all questions are safe to ask than risk alienating or hurting a student by mistaking a serious question for something intended to disrupt class.