The Wiki entry on the critics could do with some correction and addition.
One interesting part of the entry is something that I had no previous knowledge of, and reinforces his political activism.
At MacColl's instigation, members(critics group) formed a sub-group for the purpose of creating and transmitting radio programmes to Vietnam, aimed at the thousands of GIs who were already questioning why they were there in the first place.[4] From 1970 to 1972 four programmes, all called "Off Limits" were made. They were produced by Charles Parker, adapting the celebrated Radio Ballad docu-drama form on which he had collaborated with MacColl an Seeger. The programmes were allegedly sent to Vietnam through the North Vietnamese Charge D'Affaires and acknowledged by Ho Chi Minh himself. In 2016 the Australian Broadcasting Company transmitted a documentary by producer Gary Bryson, who had worked with Parker, telling the story of these forgotten programmes and the people who made them.

http://www.talkinghistory.org/
scroll down until:Segment 2 | Earshot: Off Limits (2016)
Download: MP3