Howard Jacobson: Why should Susan Boyle have to curry favour with this squalid culture?

It's tyrannical to signal that only the sveltely sexy are worthy of our attention

Oh God, she dreamed the dream. She had to, didn't she. She just had to dream the dream. Sing it, be it, live it, dream the dream and have the dream dream her.

Once, in decorous simplicity, we lived a life and then we died a death. We reserved the coupled verb and noun for the big occasions. Now we fill the space between life and death with mawkish dream dreaming, and when we dream the dream in public we don't just dream our own. We dream the nation's. We dream the planet's. If there is life in outer space you can bet your life it's dreaming the dream – the only one dream anyone's dreaming right now and that is that you'll somehow get to be on telly singing I dreamed a dream and in the act become the dream.

Try to break this circle and you'll go mad. Best just to hop on to the dream and dream it. This is shlock's ultimate victory. Dream the dream or you're a dead man. What do you suppose Ahmadinejad sang in the shower after socking it to the Swiss? "I dreamed a dream."

I was away when all this was going on. Lying in the sun, clearing my mind, reading a masterly novel called Karoo by Steve Tesich. If you haven't read Karoo, read it. Drop whatever else you're reading. It won't be as good as Karoo. It certainly won't be as funny. Genuine funny, so funny you can't breathe, because only a truly calamitous novel can ever be a truly funny novel. And Karoo is a novel of more calamity than one can bear to read. In the final chapters you wonder how the novelist could bear to write it. And he couldn't. He died before the novel was published. A writer in his fifties who imagined calamity.

As I said, dream the dream or you're a dead man.

Karoo is a novel about Nothingness, what the hero Saul Karoo calls The So What of the Soul, the nihilistic state one reaches when it becomes clear that life has reduced itself to Entertainment, to whatever will sell or feel good, every complexity or vexation ironed out, just the bare bones of a mawkish love story left to move the millions. And not even the bones, for they too have been picked clean.

I don't know what will kill us off as moral beings first: kowtowing to fanatics, wittering about twittering, reading the collected fiction of Katie Price, or mawkishness – but mawkishness is winning. Everything about Susan Boyle's rise to dreamdom is horrible. I mean truly horrible. I mean loathsome. It wasn't a dream she dreamed, it was a nightmare.

Against Susan Boyle herself I have nothing harsh to say. She looks somewhat odd and old-fashioned, her hair's a fright and her dress of choice is a length of curtaining tied with a ribbon from a chocolate box. So what? Half the women over 40 in England once looked like that and about a quarter of them – the ones who haven't had their breasts enlarged or their buttocks grafted on to their faces – still do. I salute them. They make the country tick. They don't read Vogue or Cosmopolitan, they somehow manage to miss out on sex, they water the flowers in the nation's churches, they headmistress problematic schools, they bake lemon drizzle cake for charity, and of course they sing in choirs.

What Susan Boyle should not have done was discuss her absent sex life with the sniggering Ant and Dec and then wiggle her hips at that soul-scoffer Simon Cowell. That act demeaned her. She consented to the freak show. She curried favour with a culture which once upon a time she and other women like her would, rightly, have considered squalid.

Not that any of this justifies the sneering to which she was subjected and which is now integral to the sort of television programme she permitted to insult her. We congratulate ourselves on how far we've come since our grandfathers thought a fun day out was a trip to Bedlam to laugh at the deranged. So sensitive to disability are we today, so careful around race and gender, that we outlaw from our discourses any word considered likely to cause offence and make jokes only at the expense of politicians and policemen.

But we are deluded. Bedlam is alive and well and we still go there to mock the afflicted, the only difference this time is that we do it on television and call it a talent contest, as though those who believe they have talent when they haven't, or have talent of the wrong sort, are exempt from common courtesy and can be derided as heartlessly as the insane once were.

It is dishonourable to jeer at people, however unlikely their ambitions. It is ill-mannered, it is cruel, it is pusillanimous, and it cynically contradicts the already cynical premise of the contract: for if we do indeed live in a "dream the dream" society, then everyone is entitled to dream it.

But worst of all it is tyrannical, every snort of Ant and Dec's, every vacant sneer of Simon Cowell's, signalling to the audience what it is appropriate to think and feel – in this instance, that middle age is preposterous, that an unfashionable appearance is a joke, that only the sveltely sexy are worthy of our attention, that music is the privileged province of the young and the young only, a fatuity which the young themselves are only too delighted to be flattered into accepting. (The truth of the matter being that the real music of the country is not being made on the pre-stuffed MP3 players beloved of truants, joggers and cyclists, but in churches and choirs and concert halls, in music schools and amateur operatic societies, around pianos in suburban drawing rooms, by people much like Susan Boyle.)

To be surprised she can sing merely shows one's ignorance. And then to be amazed into extravagant appreciation of what is an averagely pleasant voice singing an averagely unpleasant song, only shows it still more. I know this is the dream dreamed to its dregs, the great clichéd denouement of every musical that's ever been made – the tear-gulping moment when doubt is wiped off every face and an unlikely star is born – but to overvalue what's ordinary is just the other side of scoffing at what isn't.

"The beauty of banality," Karoo calls it. A beauty to which no one is immune, especially if it "eases the pain of being who one is". We're all in the Nothingness business together. What's cynical is to pass this Nothingness off as Something. And then to sell it as a dream.