Last week, I was reading Word, the culture primer for time-poor ageing hipsters, a midlife crisis in magazine form. Apparently, in December, the Tory feminist MP Louise Mensch, (whose ill-judged jokes about Occupy protesters on a recent Have I Got News for You sank slowly and silently like quern stones dropping down a deep Cotswold well) took David Cameron to see Gillian Welch, the alternative country pioneer. But should horrible people be allowed to go to cool stuff and ruin it for nice people?

Illustration: David Foldvari

I loved Gillian Welch. Once. "I Dream a Highway", from 2001's Time (The Revelator), occupies a hazy space where mountain music dissolves into visionary minimalism, while "No One Knows My Name" explores brilliantly the social weightlessness of adoptees. But now David Cameron has tapped his Tory toe to it. Roy Chubby Brown recently spoke movingly to the Morning Star about trying to discourage the English Defence League members in his audience, who had missed the irony in his "I Am Asylum Seeker" song, and Kurt Cobain killed himself when he realised his followers included sports fans. But Gillian Welch, who now plays to politicians, has neither attempted to police her crowd, nor had the decency to remove herself by violent force, as an ongoing concern, from the marketplace.

And so now I have to throw all my Gillian Welch CDs away. And her partner's solo album. And the great album they made backing Robyn Hitchcock. Scratch them and smash the cases and shred the sleeves and throw them in the bin with all the dirty nappies and the soiled underwear and the dressings full of blood and pus. And it's a shame. Because I loved them. (I'll keep the rare bootlegs, obviously, and illegally download the albums proper if I miss them. Gillian Welch, David Cameron's performing pig, no longer deserves payment.)

Why was Cameron there anyway? Welch's music is not the music of library closures and the stoppage of disabled babies' free nappies. Great art ought to be incomprehensible to the dead-hearted politician. But then Ken Clarke comes along, with his brilliant Radio 4 Jazz Greats. Were his real parents bereted beatniks, who abandoned him as a baby in a golf club toilet to be raised by Tories?

What soul mates can jazz-loving Ken Clarke possibly find at Tory conferences? I imagine him, sitting alone in the hotel bar, nibbling at night a grey pie, his suedes fading, with Art Pepper solos spinning inside his lonely Tory head. I'll be your friend, Jazz Ken. Perhaps Ken's happy to be part of the party of penury, hoping decades of decay will inspire a generation of black kids to hard-bop their way out of the ghetto, generating more jazz to enthuse about on Radio 4.

It is inappropriate of Ken Clarke to love jazz, and cruel of David Cameron to attend a Gillian Welch show, or indeed any live event except sport, which is of no value. It must be obvious to him that the majority of fans of anything good would despise him and that knowing he was in the room would foul their experience. But the fact that David Cameron selfishly chooses to attend anything ever shows how little he appreciates the financial sacrifices ordinary people make to go out and reveals the abject contempt in which he holds the electorate.

For David Cameron to attend a Gillian Welch show is the equivalent of him standing in front of another modern American great, say Edward Hopper's Nighthawks, and daubing it with his own faeces. "No One Knows My Name", especially, occupied a special room in the house of my heart and now David Cameron has blundered all around that house in his Bullingdon Club blazer, drunk on champagne, with dog muck on his spats, smearing it on everything I hold dear, and telling me to "calm down" while I plead with him to stop.

The first time I personally was confronted with the moral dilemma now known as Welch's Hot Potato was after a performance I directed at the National theatre, when I suddenly found my hand being shaken warmly by Michael Portillo. At first, I assumed it was the Cuprinol wood goblin, but then I realised I had touched a Tory and so I ran to the kitchens and plunged my hand into a pan of boiling water, before cutting it off and throwing it into the Thames. Dead fish floated upwards and the river foamed with much blood. But I have since met the charming Michael, and his painfully shy wife, Diane Abbott, on BBC TV's This Week, where he apologised for my stump and asked me to accompany him to the Greco-Roman wrestling at this year's Olympics. (I also worked with Ann Widdecombe once, who sadly was a lout. But then you should never meet your heroes.)

My second experience of Welch's Potato was in 2004, when I had co-written the libretto of an opera, and it's detailed in my second book, Hypocrisy Excused (Faber £7.99). Our PR woman announced Cherie Blair was coming to see the piece and that we would all stay and meet her. (These days, I doubt PRs would want the toxic Blairs coming near their brand. It would be like boasting that your premiere had been attended by the Moors murderers.)

Blair's Iraq war was in full swing and I told the PR I wouldn't glad-hand a warmonger's wife. "If it makes any difference," the disappointed woman said, "Cherie will be accompanying her friend, the head of Scope." I accepted the idea that the warmonger's wife being with a charity worker equalled a kind of moral carbon trading, where wheelchair provision balanced out child-bombing, but I did not want to meet Cherie Blair.

But then, did not Jesus sup with the tax gatherers and prostitutes? And so as Jesus supped, should I not sup also with the woman from Scope, and Cherie Blair, even though when she supped, Cherie Blair's weird flat lips were bound to look extra creepy? No. On this occasion, Jesus was wrong. Cherie Blair could go sup herself. But to avoid making a fuss, I just quietly went home early without telling anyone, Welch's Potato discreetly dropped.

Did the hot potato of David Cameron's attendance burn the palm of Gillian Welch? Did she care that the Bullingdon Bruiser bopped to that bluegrass beat? Whatever, it's over for me and Gillian Welch now. Goodbye my country girl, and thanks for all the memories. Let the dead bury their own dead, drive the plough over their bones, and let's pretend it never happened. Scorch the earth and never look back. And I've a new three inches on my overcrowded shelves.