Well mostly it comes from my memories of going to the pub before internet adoption was wide spread, Idiots were always the majority but you couldn't prove them wrong and it was difficult to find anyone that would dare express anything but the dumbest groupthink opinion. Like even as late as the start of the Iraq war the level of discourse was unimaginably dumb even compared to your average Facebook group today.

I'd actually date it back to UUCP and BBSes exchanging batches of messages once a day or so. The days of routing by bang path.