Here is what the story for yesterday's demonstration should have been: half a million marchers, in the largest show of labour union strength in decades, turn out to oppose the government's draconian cuts.

Here is what the story became: a few hundred anarchists, many dressed in black, trashed businesses and clashed with police on Oxford Street and in Trafalgar Square.

The anarchists, calling themselves the black bloc, stole the headlines from the 500,000 other protesters who'd travelled from all over the UK to express the refusal of millions to accept austerity as the consequence of a crisis they did not create.

All this has made me recall the favourite cartoon character of the Industrial Workers of the World publications, which, in its heyday 100 years, ago featured a comic-strip figure named "Mr Block", whose head was a giant block of wood. Mr Block, a particularly daft worker, would try to improve his lot in life, but he would invariably go about it in the wrong way. He would refuse to join a union. He would refuse to go out on strike. He would try to please his employer. And he never wised up.

These days Mr Block would be found in the black bloc. Mr Block would wear a bandana for a mask. He would fancy himself a threat to capitalism. His ears would be wide open to the whisperings of provocateurs. He would confuse vandalism with radicalism. He would never wise up.

These self-styled "revolutionary anarchists" are young and not, by and large, workers. They have at least enough money and privilege to risk a night or two in jail and to pay the fines. And they are as daft as Mr Block.

They fail to value the far more important outpouring of humanity seen on the streets yesterday. Railroad unions and fire brigades, office cleaners and university staff, children, families, and students, all made their voices heard. They carried colourful banners, works of great beauty, sewn with care in weeks of anticipation. They called for higher taxes on the super-rich and corporations rather than gutting social services and education. Some even chanted for what the Industrial Workers of the World always wanted: a general strike.

Meanwhile the black bloc protester is far too busy with his wonderful self to notice the working classes. He feels brave. He sprays an A on the wall. He hurls paint balloons. He whacks the shields of policemen who earn less in a year than a banker does in a day.

Then he goes home to watch himself on the telly, and scratches his head when the most of the press reduces the day to hooliganism. He laughs that his antics lead the news rather than the massive demo. He thrills that the same police who kettled peaceful students didn't bother to contain him.

And he wonders why capitalist extremes continue uninterrupted.