Hi Sarah,
I really enjoyed your singing of it in South Brent. It is a wonderful song. The mood & phrasing take me straight to Dave's 'January man' and also some of Sydney Carter's songs. There is a feeling of being done to - in January man by the inevitability of the cyclical forces of nature and in Easter Tree, man does to man (is this also inevitable?). So, although I think there are broader sad, dark allusions reflecting on the nature of the world, I agree that the main allusion is to man's inhumanity to man through what he does and has always done to individuals from Christ to every hanged murderer. It remains, for me, applicable to what is still being done in our name or in the name of justice in various parts of the world. For me the last line the stain upon the stone is the shame which is left for what has been done.
John
PS. If Dave Goulder can contribute, I would be very interested in his own thoughts.