MacColl and others worked on the basis that. unless you had a physical problem, almost everybody could become a singer

If that is what he thought then I am sorry but he was wrong. MacColl himself was no great shakes as a singer, but that is only my opinion, years and years ago, I only ever listened to MacColl sing to pick up the lyrics, there was not one single song he sang that others (e.g. Luke Kelly) didn't perform and sing far, far better (Same goes for Bob Dylan who I have always regarded as a very poor singer)

He qualified it be saying, if you want to be a better singer you have to put in the hours

The first statement makes what he states here ridiculous, you first have to be able to sing before you can become a "better" singer, especially if you sing in public.

The ability to sing is a natural talent, it is a gift that once recognised can then be built on. The "anybody can sing" school must bear the blame for the absolutely abysmally poor standard of performance you come across in UK Folk Clubs - and no, running workshops within clubs is not the answer if you cannot sing, you cannot sing, best not to impose your shortcomings on an unsuspecting public - they don't deserve that degree of disrespect.