I am sure you are right that was at the back of Pete's mind when he made that comment Harvey. I also agree that it's possible to be funny while serious at the same time - and serious and entertaining as well. I heard Danny Abse read when I was at college and found him very engaging.
Not all funny songs have a serious point behind them though. I think the writers simply enjoy the craft of putting words together in a way which they know is funny - Noel Coward, Flanders and Swann,etc. Personally I like both, but I think there are certainly writers who would never allow songs to slip from their pens if they felt they were merely frivolous. I guess I was thinking aloud and wondering - does that make them lesser writers?