Paul Vallely: Clarkson is a victim of his own values

We should never, of course, condone vandalism. But it was hard not to feel that there was something apt in the news that the fence had been hacked down around the £1.2m lighthouse holiday home belonging to Jeremy Clarkson on the Isle of Man. The boorish culture that the Top Gear presenter celebrates so exuberantly has come back to bite him on the bum.

It's important not to get this out of proportion. The "grim discovery", as one portentous tabloid dubbed it, that vandals had pulled down the cliff-top fencing comes at the end of a six-year right-of-way dispute with local ramblers in the 40 acres of coastland Clarkson and his wife have bought on the picturesque Langness peninsula. The government of the island has ruled in the walkers' favour and the dispute is now before the High Court. But clearly some disgruntled locals have decided on a bit of unilateral ramblers' revenge.

Clarkson's wife, Frances, speaking from their family home in the Cotswolds, said she felt they were being targeted. "It's not the first time it's happened. It makes me feel rather sick. It's upsetting," she told journalists. But the celebrated wit of the man himself, who has complained in the past about the island's "militant dog walkers", seemed momentarily to have deserted him. He was reported as being unavailable for comment.

We see a lot of Jeremy Clarkson in our house. Endless repeats of Top Gear appear to be the default option on our 11-year-old's preferred channel, Dave, "the home of witty banter" as it calls itself – in a tag that seems as convincing as those lines in dating magazines which proclaim the advertiser to be possessed of a Good Sense of Humour. Then there is the programme's latest BBC2 series, which in some weeks is the BBC's most popular show. Top Gear is the most watched programme of the year on iPlayer, and is broadcast to more than 100 countries, reaching 300 million viewers round the world.

You can see the attraction. You start with the obvious "speed thrills" premise of driving round Europe in a Bugatti Veyron. But Top Gear long ago ventured further into an adolescent-male fantasy world – destroying its most hated cars by crushing them with a tank, catapulting them with a trebuchet, dropping them on to a caravan or shooting them up with a helicopter gunship. All of which is done against a failsafe formula of races between the programme's three protagonists in increasingly exotic locations. All that has changed, as the last decade has passed, has been Clarkson's girth, the ageing of the baby-faced boy-racer Richard Hammond and the length of the hair of the group geek, James May.

Hammond and May are essentially the straight men to Clarkson's gagster. He is genuinely funny. But his humour is rooted in the caricature of a lovable saloon-bar rogue. He is a white middle-class male not-afraid-to-speak-his-mind-in-a-world-of-political-correctness-gone-mad. Like Dick & Dom shouting "bogies" in the polite quiet of an art gallery, the point of his vulgarian humour is to cause offence.

So he is rude about cyclists, caravans, vegetarians, women, gays, health and safety, and green activists whom he dubs "eco-mentalists" and says in a previous life were failed trade unionists and "CND lesbians". Foreigners, and their stereotypes, are all fair game: Korean car designers eat dogs, Mexican motors are lazy, German cars have their satnavs set to invade Poland and Malaysian vehicles are built "in jungles by people who wear leaves for shoes".

He suits the action to the words. Rather than enthusing over lower-emission sports cars, Clarkson will drive a 4x4 through a Scottish peat bog, wreaking destruction that will take decades to make good. At one point he so resisted the notion that cars, or any other human activity, were accelerating climate change that some MPs wanted to summon him to a select committee to explain his "curious and misguided attitude to the real and major threat posed by climate change".

But this is not the satire of Loadsamoney or Alf Garnett. Clarkson means it. Thus Gordon Brown, then prime minister, was a "one-eyed Scottish idiot" and, in one unbroadcast warm-up, "a silly c*nt". There is about him the casual cruelty of the public school bully. (He was expelled from Repton.) It is the core of his relationship with pretty-boy Hammond and clever-boy May.

Yet Clarkson is clever too; he plays the misogynist homo-allergenic xenophobic boor with the highest level of articulacy. Clarkson's defence is not satire but irony. In a post-feminist world, he implies, it is now acceptable to say: "You'd pay half-a-mill to spend some time with a girl who had Mrs Thatcher's drive, Victoria Wood's sense of humour and Scarlett Johansson's body, would you not? Well, that's what this car is." But he fails to understand, or perhaps to care, that hundreds of viewers will complain when he jokes about lorry drivers murdering prostitutes – or says of high taxes on supercars: "That's not taxation. That's rape".

"I don't believe what I write," he once said to Alastair Campbell, "any more than you believe what you say." He has different faces for different audiences: the reactionary buffoon in his Sun column, the funny gin-and-Jagster on Top Gear, the droll raconteur on QI. His failing is that, as the years pass, he has become a caricature of himself.

None of this would matter were it not for the fact that some people mistake the cartoon for an archetype and take him at his word. There are those who find his lazy humour and casual racism unexceptional. Or think his self-centred dismissal of speed cameras and road bumps is justified. Or are amused by his contemptuous attitude to women or his calling gays "ginger beers". Or endorse his use of the word "gay" for anything that does not work very well. Or admire his insistence on smoking even more cigarettes than usual on National No Smoking Day. Or accept his neanderthal views on global warming as readily as his vocabulary about "being a true petrolhead".

Having a boy on the edge of pubescence in our house, we understand the lure of The Dangerous Book for Boys and the constant need to be climbing up things or swinging off them. We see, too, how Jeremy Clarkson's self-absorption offers an attractive adolescent model of defying authority, disregarding rules and trampling carelessly on the sensitivities of others. Perhaps it is a phase through which we all must pass, and will enjoy on the way. But it does not offer a mature destination.

For it ends with the kind of high-octane self-righteous indignation that Frances Clarkson saw visited on her luxury holiday home while her husband was away on the latest Top Gear world tour. It is reaping a whirlwind of sorts. But when the monsters you have created come round and turn their attention on you and yours, suddenly, it's not quite so funny. Irony, eh? You've got to laugh, intcha.