Conspiracy theory is a phrase used to dismiss narratives that are critical of the deep state. A person who espouses such theories is derided as a "conspiracy theorist"
According to Aaron Good, the phrase was seen as reasonable during FDR's Progressive Era when public suspicion of economic elites was high.
However, during the 1960s the CIA (through Operation Mockingbird and other means) sought to use the phrase to dismiss people who are critical of the government and the economic elites behind them.[1]
ProleWiki aligns itself with the CIA against these "conspiracy theories", by only using absurd examples of such theories, such as flat earth, etc.[2]