Of all political perversions, racism is the most odious. Oppression on grounds of politics or religion or even sexual orientation at least allows the victim the possibility of dissimulation, of denying any affection for capitalism, Catholicism or homosexuality while retaining allegiance in the privacy of the heart and soul. Stalinism, to be sure, demanded inward as well as outward obedience and gave rise to the concept of "thought crime", thus creating a new landmark in the history of tyranny. But even that left people with a glimmer of hope. Racism allows none, because its targets can never disguise themselves and do not have the life-saving options of betraying their consciences: one may recant a heresy, but not a skin colour or other racial feature. That is why calculations of the numbers killed by Stalin and Hitler are beside the main point: that the Nazi tyranny deserves special opprobrium because, both in theory and practice, racism was its raison d'etre. That is also why the apartheid regime in South Africa drew particular condemnation; why we regard the murder of Stephen Lawrence as peculiarly vile; why we think special laws are necessary to restrain the incitement of racial hatred. And it is why European leaders are so alarmed by the rise to power in Austria of Jorg Haider's Freedom Party.

The difficulty is to judge the extent to which Mr Haider is truly a racist. His Freedom Party is not driven exclusively by racism as the Nazi and apartheid regimes were. But we know that Mr Haider's parents were Nazis; that he has never distanced himself from his family past; that in 1986, on a pan-German platform, he launched a successful coup against the more liberal wing of the Freedom Party; that in 1991 he praised Hitler's "orderly employment policy"; that in 1995 he addressed a reunion of the Waffen-SS and accorded it "honour and respect"; that only three years ago he proposed that a third of all foreigners working in Austria be sent home.

It may be argued that British politicians and newspapers, in their harsh, even vitriolic, language against asylum-seekers - now almost invariably qualified as "bogus" - talk much the same language as he does, and that his anti-Europe rhetoric is virtually indistinguishable from that of our Conservative Party. It may also be argued, as Michael Elliott of Newsweek has done, that it is rather odd for world leaders to treat the unarmed fascists of Austria as pariahs while they embrace the armed fascists of Northern Ireland.

Yet, despite these reservations, the European Union is right to register its disapproval; a party that trades at least partly on racism has entered the government of a member state. The political sanctions may be no more than gestures - the withdrawal of all but "technical" briefings from Austrian ambassadors, for example - but gestures are precisely what is needed at this stage. What needs to be brought home not just to Austrians but to people of all countries is that, whatever their frustrations with the established political system, recourse to extreme right-wing leaders, with openly racist or xenophobic agendas, is a dangerous game. It is all very well to insist that people should have an absolute freedom to vote for whom they like, just as we may insist that they should have an absolute freedom to say or write what they like. But racism is a special case, because it ultimately denies to a whole group even the right to keep themselves to themselves. Britain and the US - though far from free of racial prejudice and discrimination - are infinitely less racist societies than they were 40 years ago. That is because respectable (elitist, if you like) opinion has compromised freedom of expression and put racism largely beyond the pale, even at the cost of some very silly examples of "political correctness".

There lies the nub of the arguments over Mr Haider. A heavy hand with racists, say some, turns them into heroes; the EU's actions will merely strengthen anti-foreigner sentiment in Austria. But its actions are equally likely to give notice, both to Austrians and to other Europeans, that the country is moving perilously close to the margins of social acceptability. Already, there are boycotts from Prince Charles and tourists alike. Though some marginal groups in Britain and America may embrace racism as a badge of defiance, it seems doubtful that a whole country would do so - a country that enjoys low unemployment, western standards of living and the benefits of international trade and travel. The EU's reactions may be called hysterical; but, with Auschwitz still within living memory, the merest whiff of racism is something that merits hysteria.