(You can click on the image for a clearer picture.)
In my defense, the communists-and-rainbows remark came over two hours into a three hour lecture, so perhaps I had let the rigor of my philosophical vocabulary slip a bit by that point. And it was intended as a tongue-in-cheek paody of the way people think Marx envisions the post-revolutionary future. No matter how hard I try to emphasize to students that we need to work our way through Marx's critique of capitalism before we can take an informed look at what he offers in its stead, everyone still wants to skip ahead to the end and condemn the "communist future" as utopian first. My remark was just a way of temporarily indulging that misconception so that we could table it and get back to the work we needed to do.
Or, at least, that's my story... and I'm sticking to it.