I believe that "...those who seem to get great joy out of piling on ...etc." do so, basically, because they perceive that MacColl was anti-rock music. Ewan made the big 'mistake' of being indifferent to (or possibly hostile to) commercial rock music just when it was beginning to swamp our popular culture - and some people have never forgiven him for it.

MacColl pushed the idea of performing traditional, or traditionally inspired, music in folk clubs at a time when some were hoping for an 'anything goes' policy in such clubs. Some of these people were just anti-intellectuals who didn't want folk clubs to be any more taxing than the latest pop hit, but others saw folk clubs as a convenient platform for launching their own careers as rock musicians. When the latter received a poor reception in the clubs (or were, perhaps, unsuccessful in achieving their aspirations) they had a tendency to blame the person who they saw as the most influential artist of the post-war Revival.

I have advanced this hypothesis before but, revealingly, have usually been met by a deafening silence.

Finally, I should like to point out that I have no quarrel with people who didn't find MacColl's work to their taste or who may have disliked his politics or disagreed with his views on folk music - you are entitled to your opinions. I suspect, though, that trolls like 'Toxic Bob', who started this thread, would have had no interest whatsoever in MacColl's war record if he had played an electric guitar and had enthusiastically welcomed would-be rockers into folk clubs!