While I hesitate to disagree with somebody with as Scots a sounding name as Douglas, as far as I have been informed by in-laws and friends, Scotch was once a term commonly used by English and Scots alike for those coming from Scotland but nowadays it is not favoured by them. My dictionary gives as part of the definition "Scotchman/woman are forms sometimes heard outside Scotland, but many people find them mildly offensive. Scottish is the generally acceptable collective term". It could be argued that terms like Nigger and Yid are contractions of Nigerian and Yiddish and, while I would agree that there is a difference between the level of offence intended and taken by these terms, all give offence to one degree or another and are best avoided, just like the term 'snobbish' when applied by an individual to a large number of people (in which case the similarly offensive term 'arrogant' springs to mind). I understand from Scots friends that the term Scotch has Socio-Historical connotations rather than Malcolm's somewhat simplistic and dismissive analysis.
Back to MacColl;
I have followed this thread with some fascination.
When I came to traditional song back at the end of the fifties the pro-anti MacColl battle was being waged fiercely even then – and many of the arguments used then are still being aired – little has changed, (except MacColl has now been dead for over fifteen years).
I picked my sides back then on the strength of what I heard. I was immediately sucked into the serious side of the revival by the Topic sea albums of Ewan, Bert Lloyd and Harry H Corbett. I became a life-long ballad devotee on the strength of the Riverside albums of MacColl and Lloyd, described by Betrand Bronson as "the most important event in the field since the publication of Sharp and Karpeles' Southern Appalachian collection."
Theme albums like 'Chorus From The Gallows', 'Shuttle And Cage' and 'Bold Sportsmen All' helped make me aware of the broad scope of traditional song, and the still unsurpassed 'Song Carriers' deepened my interest and understanding. The Radio Ballads helped place the language of traditional song into a social context. The few times I met MacColl back then, I was impressed by someone who regarded folk song as an art form which deserved to be treated just as seriously as any other art form.
Down the years I have heard MacColl and Seeger give varying qualities of performance, but I can never remember hearing them sing badly, come unprepared to a club evening, or, as I have heard elsewhere, treat the songs, or the audience with contempt - (I did once see one of the 'stars' of the revival at a club in Manchester, stagger onto the stage drunk and vomit over someone in the front row. I've lost count of the number of times I've heard performers of traditional songs take the piss out of them as being quaint and risible).
While most of these 'stars' were getting on with their own careers, MacColl was running a weekly workshop for less experienced singers. The work of this workshop was helping broaden our understanding of traditional song through its researches into the London repertoire, the Waterloo – Peterloo project and the club feature evenings they were putting on combining song, poetry and prose readings.   
I found that MacColl's politics broadly coincided with my own. In the early days he was lending his support to the peace movement and the trades unions. When Apartheid thugs massacred unarmed Africans, MacColl responded by pointing the finger with his 'Ballad of Sharpville. He was one of the prime movers in the 'Folksingers For Freedom in Vietnam' campaign and helped draw attention to the atrocities that were taking place in that country. Throughout the Thatcher period when she and her government were tearing Britain in half and teaching the workers their place in society, it was MacColl's outpourings that gave many of us a boost and when she used the British police force as a private army against striking miners his support for those strikers was unwavering. How politically effective in changing the political situation is debatable, but as far as those of us who were involved were concerned they certainly helped keep us going.
That MacColl's and my father's generation were guilty of errors of judgment is of course true; as Barrie Roberts rightly suggests, isn't everybody capable of being wrong? An excellent history of the British Communist Party was published about ten years ago which deals fairly comprehensively with who knew what and when about Stalin.
On Thursday night I watched a film based on the experiences of three British Asian in Guantanamo and yesterday morning I woke up wondering why there weren't thousands of people on the streets of Britain and America protesting at the atrocities that are being committed in their name. Not too far from here there are weekly flights landing at an airport carrying torturers and their victims to countries where these activities can be continued with impunity, yet, as I write, the greatest visible response is that four people are on trial for the heinous crime of unfurling a banner in the departure lounge of that airport.
Each day in the national press we are regaled with yet another account of children being abused by paedophile priests – the main reaction – a constant stream of letters complaining about the ordeal these priests are being put through by these revelations.
A deafening silence hangs over the systematic ethnic cleansing that is being carried out on our Traveller population. With very few exceptions, those who don't actively support the policy pass by on the other side.
I have no idea why such things happen in our 'enlightened' society; but one thing I am certain of; I know exactly where MacColl would have stood on these issues.
There was a song dating back to the 1930s Harlan County mining wars which was popular in the early days of the revival – 'Which Side Are you On?'. Anybody who ever met MacColl was left in no doubt as to which side he was on.
If, as has been suggested by one 'highly articulate' individual, MacColl was a "total wanker", it seems to me that what the world (and traditional music) needs now is a few more "total wankers" like him.