Yes, more's the pity. Blake's Jerusalem is a great work, like much of his stuff, but you have to hear the cadences of maudlin reformist nationalism in the hymn's adoption by the British labour movement. It is also sung at the last night of the proms and at the Oval cricket ground. I can remember being in trafalgar Square around 1990 at a 'defend the national health service' demonstration and the crowd (which was considerable - the trade union leaders still had pulling power in those days) sang Jerusalem at the dusk. The mood was elegiac, defeatist, mournful.
That's why I can't listen to Billy Bragg - that's his voice in there. You can hear it in Pete Docherty, too. Forgiveable in Ray Davies and Ian Dury, who always shift a gear from nostalgia to mockery (think of the Village Green Preservation Society, or Billy Bentley). The fag end of Pre-Raphelite, romantic anti-capitalist Patriotism. Why the British working class was defeated, really. Too much Billy Bragg, not enough Easterhouse.