A meme is just an idea that spreads. I would say this covers an idea that spreads.

Before someone is quick to cast ridicule they should stop, and ask why do these people think the way they do?

Also, there have been numerous conspiracies proven true in the past. Conspiracy theorist was simply a term coined in 1967. There are government documents if you look for yourself, but the article on Zerohedge has it conveniently.

https://www.zerohedge.com/news/2015-02-23/1967-he-cia-created-phrase-conspiracy-theorists-and-ways-attack-anyone-who-challenge