Why anybody should treat a piece of opinionated hyperbole coming from the mouth of a philologist with 'reverence' I do not know.

Bawdy songs must have been part of lower class culture, there are periods when we know for sure they were part of upper class culture and there is plenty of that sort of thing in Chaucer and Shakespeare and Boccaccio. Which reminds me to try to find out did Child include the late 17th century poet John Wilmot the Earl of Rochester in his collection of Eng Lit or was that left out?