Just because someone is a good artist - it doesn't mean they will share your political views.

Roy Porter was a brilliant poet of the 1930's and translator of Baudelaire, but he was an ardent Catholic and supporter of Franco.

TS Eliot wrote a letter to the papers in support of the hanging of EDith THompson.

They were both gifted writers.

I like to think of MacColl as part of that wonderful optimism and artistic renaissance that sprang from the aftermath of World War 2. Plus the uneasiness that came with the country voting Conservative. The interest in folksong as the birthright of the British Isles - you find it in Chips With Everything by Arnold Wesker when (unlikely) the whole of the RAF mess joins in a chorus of The Cutty Wren - much to the discomfiture of the officers, who go off in a huff.   Also you find folksong John Arden's plays. Sergeant Musgrave's Dance, and Armstrong's Last Goodnight is a play based on a folksong that many of us will have encountered in folk clubs.

What I'm trying to say is - I think its about a spirit that was abroad in England at that time. The Radio Ballads and much else in Ewan's work. The zeitgeist of the times, if you like. I don't see it as a dedication to Marxism in the abstract sense.
That actual point in time, socialism was in the air. Like in Tudor times - people found it easier to believe in God. In that period - people found it easier to believe in the prromise of a better life offered by socialism.
Ewan was a man of his times. I sort of envy him in that.