I thought it was about Nutopia?
I don't think it's promoting communism, I think Lennon did agree with some of the communist ideas but that in and of itself isn't a bad thing. The idea of Communism isn't a bad one. It just doesn't work in practice. Lennon was a dreamer, and an idealist. A doped up Dreamer and Idealist. He was only imagining his perfect world.