Ask them:
What is the term for the difference in tonal quality heard when an approaching object (like a train) passes and is moving away?
you could even make it multiple choice:
A.) Gravity
B.) Speed
C.) the Doppler Effect
D.) the Poseiden Adventure
Thats’s too easy. Ask him to explain the chemistry of so-called AGW.
there will be 300 rebuttals the next day containing different “facts”, but that all say he didn’t get it quite right.