I am just barely old enough to be a former semi-fellow-traveler myself (then, in high school, I read Orwell).

Stalin shed plenty of sympathizers on account of
*the Moscow trials,
*the alliance with Hitler,
*the invasion of Finland,
*the subjugation of eastern Europe.
(I am bad on dates, but I think I have them in the right order anyway. I leave aside such messy subjects as the Spanish War.) Anybody who stuck with him till Khrushchev discovered his wickedness, as MacColl seems to have done, may reasonably be accused of excessive piety, IMO.

Nevertheless, if the 20th century were about to be erased & I were allowed to pluck one singer out of it, he would be the one.