You took the opportunity to educate him a little and he seems to have accepted it as legitimate and acceptable. That's the way we should always handle that type of thing, be it from a six year old, a sixteen year old or a sixty year old.
Good job!

The exception is when it's not curiosity or ignorance and the comment or question comes from a narrow and preconceived opinion that just won't be changed or lessened. Then, light them up and walk away.