I find conspiracy theories to be almost like some sort of sci-fi / fantasy lore.
I love watching stuff like Ancient Aliens, I know it is complete nonsense but it is fun laughing at all the begging the question they do.
My other half believes in some super natural stuff such as horoscopes etc and she gets a bit annoyed at me and my brother taking the mickey out of it but that is about as far as the "harm" goes with most of this stuff.
Trying to stop people believing in crazy things just isn't possible and actively trying to suppress it online will just make it worse.