The programme did give the impression that the Critics Group got more and more "critical" as it went on. Probably why it lasted as long as it did.

I rather got the impression that the Roberta Flack cover was there because it was an example of a song that was very different to the kind of songs the Critics Group were (allegedly) being encouraged to write.

I can't speak for the programme makers, but I'm guessing it was inserted into the programme to make the point that, despite a great deal of what he said and did, Ewan MacColl could actually write a decent love song when he wanted to. I think it's a shame he didn't write so simply more often.