A really good question. Someone should do a careful archival study of when pedophilia became the go-to accusation; did it start with Q or was it already there? But in a way it fits a pattern 1/ https://twitter.com/john_sipher/status/1348650864010014725

Hofstadter's "The paranoid style" noted the preoccupation of conspiracy theorists with sex 2/ https://harpers.org/archive/1964/11/the-paranoid-style-in-american-politics/

Relevant passage 3/

In the past this might have involved fantasies about lurid affairs and homosexuality. But when your standard-bearer is Trump, the former doesn't work, and homosexuality doesn't carry the cultural taint it used to. So what's left? 4/

Pedophilia is one sin that remains forbidden and unclean no matter how culture changes. And my guess is that very few people on the right know the story of Dennis Hastert ... 5/