I don't think that the hoax believers do have a "foothold in mainstream thought."
No one I know personally believes the moon landings were hoaxed.
It's possible that I suffer from surrounding myself only with the well-educated, but their actions in other matters don't really lend credence to that counter-argument.
What you see on the web and might hear on a very late-night radio show is in my opinion a very vocal and very tiny minority. The rest of popular culture views it as the sort of thing that "nutburgers" believe in, and doesn't give it any serious attention.

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