Imagine
When I was a teenager, I had troubles with perceiving oral English. Actually, I still have them.
Because of that (and lack of real interest, to be honest), I thought Lennon was depicting some apocalyptic post-nuclear devastation. There isn't this, there isn't that. People who can't think of anything beyond today's pressing needs. A melody nicely setting off the depressing scene. And in the end: "You may say I'm a dreamer" - clearly a piece of grim humor alluding to those evil guys who hasten the disaster.
Art is power.
(Evoked by an article analyzing the song as a manifesto of the values behind political correctness, in the context of the riots in France)
Will be eventually tagged as non-linguistics.