>>53091637flat earthers don't exist. more specifically, it's an artificial, manufactured conspiracy theory created to make actual theorists look stupid.
the earth is obviously round, as
>>53091123 explained, and that is primary school education. the idea of a flat earth is inherently absurd and usually associated with the uneducated, ignorant mindsets of the early medieval period.
the idea is that if someone starts pushing a theory that may have some legitimacy, say mkultra, he'd instantly be labeled a conspiracy theorist and that, in the mind of an average citizen, would be equal to a "delusional flat earther". in fact, it's fairly common of a response to any theory for an average citizen to say something along the lines of "yeah, and the earth is flat".
of course, if a theory ends up being proven right, the denial is quickly memory-holed, and a whole dictionary of weasel words, excuses and so on is applied. but that is a topic for another time.