Is Susan Boyle ugly? Or are we? On Saturday night she stood on the stage in Britain's Got Talent; small and rather chubby, with a squashed face, unruly teeth and unkempt hair. She wore a gold lace dress, which made her look like a piece of pork sitting on a doily. Interviewed by Ant and Dec beforehand, she told them that she is unemployed, single, lives with a cat called Pebbles and has never been kissed. Susan then walked out to chatter, giggling, and a long and unpleasant wolf whistle.

Why are we so shocked when "ugly" women can do things, rather than sitting at home weeping and wishing they were somebody else? Men are allowed to be ugly and talented. Alan Sugar looks like a burst bag of flour. Gordon Ramsay has a dried-up riverbed for a face. Justin Lee Collins looks like Cousin It from The Addams Family. Graham Norton is a baboon in mascara. I could go on. But a woman has to have the bright, empty beauty of a toy - or get off the screen. We don't want to look at you. Except on the news, where you can weep because some awful personal tragedy has befallen you.

Simon Cowell, now buffed to the sheen of an ornamental pebble, asked this strange creature, this alien, how old she was. "I'm nearly 47," she said. Simon rolled his eyes until they threatened to roll out of his head, down the aisle and out into street. "But that's only one side of me," Susan added, and wiggled her hips. The camera cut to the other male judge, Piers Morgan, who winced. Didn't Susan know she was not supposed to be sexual? The audience's reaction was equally disgusting. They giggled with embarrassment, and when Susan said she wanted to be a professional singer, the camera spun to a young girl, who seemed to be at least half mascara.

She gave an "As if!" squeak and smirked. Amanda Holden, the female judge, a woman with improbably raised eyebrows and snail trails of Botox over her perfectly smooth face, chose neutrality. And then Susan sang. She stood with her feet apart, like a Scottish Edith Piaf, and very slowly began to sing Les Miserables' I Dreamed A Dream. It was wonderful.

The judges were astonished. They gasped, they gaped, they clapped. They looked almost ashamed. I was briefly worried that Simon might stab himself with a pencil, and mutter, "Et tu, Piers, for we have wronged Susan in thinking that because she is a munter, she is entirely useless." How could they have misjudged her, they gesticulated. But how could they not? No makeup? Bad teeth? Funny hair? Is she insane, this sad little Scottish spinster, beloved only of Pebbles the Cat?

When Susan had finished singing, and Piers had finished gasping, he said this. It was a comment of incredible spite. "When you stood there with that cheeky grin and said, 'I want to be like Elaine Paige', everyone was laughing at you. No one is laughing now." And it was over to Amanda Holden, a woman most notable for playing a psychotic hairdresser in the Manchester hair-extensions saga Cutting It. "I am so thrilled," said Amanda, "because I know that everybody was against you." "Everybody was against you," she said, as if Susan might have been hanged for her presumption. Why? Can't "ugly" people dream, you flat-packed, hair-ironed, over-plucked monstrous fool?

I know what you will say. You will say that Paul Potts, the fat opera singer with the equally squashed face who won Britain's Got Talent in 2007, had just as hard a time at his first audition. I looked it up on YouTube. He did not. "I wasn't expecting that," said Simon to Paul. "Neither was I," said Amanda. "You have an incredible voice," said Piers. And that was it. No laughter, or invitations to paranoia, or mocking wolf-whistles, or smirking, or derision.

We see this all the time in popular culture. Do you ever stare at the TV and wonder where the next generation of Judi Denchs and Juliet Stevensons have gone? Have they fallen down a Rada wormhole? Yes. They're not there, because they aren't pretty enough to get airtime. This lust for homogeneity in female beauty means that when someone who doesn't resemble a diagram in a plastic surgeon's office steps up to the microphone, people fall about and treat us to despicable sub-John Gielgud gestures of amazement.

Susan will probably win Britain's Got Talent. She will be the little munter that could sing, served up for the British public every Saturday night. Look! It's "ugly"! It sings! And I know that we think that this will make us better people. But Susan Boyle will be the freakish exception that makes the rule. By raising this Susan up, we will forgive ourselves for grinding every other Susan into the dust. It will be a very partial and poisoned redemption. Because Britain's Got Malice. Sing, Susan, sing - to an ugly crowd that doesn't deserve you.

• This week Tanya watched Atomic Train, a 1999 movie masterpiece about a runaway train carrying nuclear material somewhere near Denver: "Wally, you're not a captain. You don't go down with the ship." "I've been living on trains for 33 years. Give me one good reason why I shouldn't die on one." She read the Qur'an in Arabic, a language she does not understand.