Prof. Dick Lipton has summarized in this post hecklers and answers at technical talks. And I obviously have one to add. Years ago I was interrupted by some elementary questions on vision at a seminar talk, from a professor who had kept himself away from vision research for some 10 years. I could recall it was about SIFT and action recognition, which were obviously still unfamiliar ten years ago. After repeated explanations and several warnings of over-timing (and the professor unintentionally not willing to put the discussion offline), my answer was
You need to update yourself!
followed by silence and laughter, and game over.