I can’t remember where I heard it, maybe a Joe Rogan clip, but he made a good point that believing that there are _no_ conspiracies is also an extreme viewpoint that is obviously wrong, given that some conspiracy theories eventually turned out to be conspiracy facts.
I don't think there is anyone who believes there are no conspiracies.
The terms "conspiracy" and "conspiracy theory" have very different meanings. This is essentially just a linguistic sleight of hand, not too different from when creationists say "evolution is just a theory". "Conspiracy theory" is somewhat unfortunate term.
Isn’t it the “deep state” and “government coverup” type of theories that are conspiracy theories? The flat earth thing is an example of that, where the theory is that “they” (the government or big globe or whoever) are trying to convince you that the world is round when it’s actually flat.
Note that the article we’re discussing specifically mentions “people who believe in conspiracies” in the first line.
Maybe not zero conspiracies in total, but academic social science does take it as axiomatic that public sector organizations never engage in conspiracies. That's why their papers always assume any belief that they might do so is automatically false and must be explained via other factors. Occasionally you see recognition that private sector actors might genuinely conspire, but never public sector.
Invariably, such papers use an ad-hoc set of beliefs that are labelled as false with no explanation or investigation. The authors just assume that because everyone they know believes something, it must be true. Ironically that's the same sort of faulty belief system they claim to be investigating.
