Okay but have you read Shakespeare? Or, for the Roman graffiti you referenced, Plautus? Or Suetonius if you want some good tabloid fodder? They're similarly crude, and while there is a much higher level of literacy and wordplay, it's... not that much different at its core. Even that graffiti, funny enough, has an example in the other direction - there are instances of graffiti in Pompeii which demonstrate a knowledge of classical literature amongst the urban masses.

My point in the end is simply that history is written by writers, and writers are not necessarily less inisane, less gullible, or less prejudiced than the general population.