Perhaps he means non academic discussions like whether vaccines actually work that you find on forums. There's loads of people doubting established facts.
Moon landing denialism is a prevalent minority belief. I think it's within the realm of possibility that the Apollo landings may one day be regarded as myth by the majority, if society (once again) takes an anti-intellectual turn. The cynical dismissal of "Hollywood faked it because of the Cold War" is a very neat and tidy meme that spreads well as it is.