The Nobel Peace Prize died in 1973, when Henry Kissinger - one of the great mass murderers of our time - became a beaming recipient. This Saturday, the Nobel Prize for Literature will join its sister-prize in absurdity when Harold Pinter collects his award by video-link. The only appropriate response to his Nobel rant (and does anyone doubt it will be a rant?) will be a long, long pause. And in that pause, we should ask a few sad questions.

How did the world's leading literary prize go to a man whose most recent works include this: "We blew the shit right back up their own ass/ And out their fucking ears./ It works. / We blew the shit out of them,/ They suffocated in their own shit!/ We blew them into fucking shit./ They are eating it./ Now I want you to come over here and kiss me on the mouth"? And - more importantly - how did a young Jewish boy who grew up fighting against Mosleyite fascists on the streets of the East End wind up as a patron of the International Committee to Defend Slobodan Milosevic?

There are two arguments against Pinter - one literary, the other political - and they are both hard to make, because, in amongst the screw-ups, Pinter has some undeniable achievements. Harold Pinter has one literary accomplishment: he imported the surrealism of Samuel Beckett, Eugene Ionesco and Luis Buñel into the staid English theatre. As the critic Irving Wardle put it, in his first play The Birthday Party, Pinter showed "how a banal Blackpool boarding-house could open up to the horrors of modern history".

At their best his plays are like a nightmarish stress-dream: unbearably primal, raw expressions of menace and fear, whose meaning is always just beyond our grasp. But with Beckett, you always know there is an elaborate existentialist philosophy underneath the darkness and chaos. With Pinter, if you turn on the light and switch off the atmospherics, you find... nothing, except a few commonplace insights: Torture is Bad and Resistance is Good. Pinter himself says "the most important line I've ever written" is when Meg's husband calls out, as Stanley is taken away, "Stan, don't let them tell you what to do." The playwright said of this unobjectionable, obvious platitude: "I've lived that line all my damn life. Never more than now." It's depressingly revealing: Pinter's staccato sinisterness does not illustrate a point; it distracts the audience from the fact his point is so banal.

But the more important case against Pinter's Nobel is political. Of course, literary prizes shouldn't be subject to a political litmus test - but the Nobel committee has explicitly said his opposition to "oppression" was a factor in the award.

So what are these politics he is being rewarded for? Ever since Pinter was a teenager, he has been relentlessly contrarian, kicking out violently against anything that might trigger his rage that day. He claims to be a man of the left, but a few wildcat strikes at the National Theatre were enough to make him vote for Margaret Thatcher, and he has shown an extraordinarily patronising attitude to the British poor, illustrated in an anecdote in Michael Billington's biography. Pinter once bumped into the tramp he had used as a model for the central character in his play The Caretaker on Chiswick roundabout. "We had a chat and I asked him how he was getting on. I didn't mention the play, because he wouldn't have known what a play was," he said. Pinter did not mention the play that was to make him millions of pounds by using this man as an inspiration. No: instead he noted to himself: "I was very close to this old derelict's world, in a way." His reason for comparing himself to a homeless person? When he was a student at Rada, he would skive off (because it was "full of poofs and ponces") and wander the streets "like a tramp". Yes Harold, just like a tramp.

But Pinter cannot be dismissed as politically worthless: this is a story with many greys. Sometimes his fickle rage has been directed against targets who really deserved it - and Pinter behaved with ramshackle heroism. In 1979, he travelled to Nicaragua to back the democratic, socialist Sandinistas against the US-backed fascist guerrillas who were besieging the country. In 1985, he spent five days in Turkey - as international President of Pen - where he met with dissidents, and spoke out against torture and state-backed murder.

The tragedy of Pinter's politics is that he takes a desirable political value - hatred of war, or distrust for his own government - and absolutises it. It is good to hate war, but to take this so far that you won't resist Hitler and Stalin (Pinter was a conscientious objector in the 1940s and described British soldiers fighting Hitler as wearing a "shit-suit") is absurd. It is good to oppose the crimes of your own government - but when this morphs into defending the crimes of others, your principles have gone awry.

When Serbian nationalism - stoked and stroked by Milosevic - began to ravage the Balkans in the 1990s, Pinter's response was simple and visceral: whatever the US and UK governments are for, I'm against. Blair and Clinton are condemning Milosevic? Right, sign me up for the defence. The committee he sits on is not simply calling for him to be given a fair trial, it is calling for Milosevic to be released on the grounds he is not guilty. It calls him: "The strongest pillar of peace and stability in this region".

So confronted with ethnic cleansing, two days' drive from Auschwitz, Pinter's response was to defend the aggressor and attack the victims. Much of the left - decent people like Peter Tatchell, Michael Foot and Susan Sontag - was calling for democratic countries to arm the Kosovo Liberation Army (KLA) to defend the ethnic Albanians from racist murder, but Pinter describes the KLA as "a bandit organisation" that was "actually" responsible for the ethnic cleansing in the region.

Watching the trial, Pinter said: "Milosevic is giving them a run for their money" and has been the victim of a "kidnapping" that has brought him in front of an illegal court. He now says his position is that Slobodan should be released until "the real criminals", Bill Clinton and Tony Blair, join him in the dock.

Human Rights Watch - and others who know something about the Balkans - have responded to the Pinter school of thought with horror. Its director, Richard Dicker, says: "This is not victors' justice - this is justice for the victims of horrific crimes. Slobodan Milosevic was at the top of the chain of command of military and security forces that wrought mayhem in Kosovo in early 1999."

Unless there is a new Nobel Prize for rage-induced incoherence, Harold Pinter's ravings should not be beamed into Stockholm this weekend.

j.hari@independent.co.uk