Here’s how the conversation should have ended:
Amateur: The Moon is made of green cheese.
Astronomer: No it's not, it's made (after oxygen) of silicon, aluminium, calcium, magnesium, and iron.
Amateur: Find me a citation that says it's not made of green cheese.
Astronomer: Here's a chart I just found in my files and uploaded which gives the composition.
Amateur: How do you know that's what it is? I say it's a chart of the composition of Pluto.
Astronomer: Understandable. Have a nice day.
The conversation was painful because the astronomer didn’t know when to stop talking.