Today Hillary Clinton has a chance to do what the BBC, most British newspapers and the rest of the political class have singularly failed to do: she can confront the Conservative party over its noxious new alliances in Europe. When she meets William Hague in Washington she can ask him why the Tories now share a Brussels bed with far-right allies most Americans would consider beyond the pale.

As the Guardian reports today, pressure on the issue is building in the US. If only we could say the same here. Not that there's been a shortage of information on either Michal Kaminski, the Polish politician who leads the new Conservatives and Reformists grouping in which the Tories sit, or its Latvian affiliate, the For Fatherland and Freedom party. We have heard Kaminski first deny, and then admit, that he wore an infamous fascist and antisemitic symbol. We have heard him explain that Poles should apologise for the horrific 1941 pogrom at Jedwabne only once the Jews have apologised for all that they inflicted on the Poles. We know that he began his political journey in a neo-Nazi organisation.

As for Latvia, no one can claim not to know that the Tories' new allies are prime movers behind the annual parades which celebrate the Latvian legion of the Waffen-SS – a band of brothers that included men who roamed the country gunning down Jewish men, women and children in their tens of thousands. For Fatherland and Freedom admire the Waffen-SS so much, they tried to get its veterans rewarded with a military pension – a move too far even for Latvia's other nationalist parties.

We know all this, yet where is the outrage? Where is the revulsion at David Cameron becoming partners with men who cheer those who fought for Hitler and against Churchill? The Guardian, the Observer, the New Statesman and now the Jewish Chronicle have been shining a light in this dark corner, but from the rest of the media there has been little more than silence.

How to explain this? Politics provides a small answer, in every sense. People can sense that power is shifting to the Conservatives, and many are anxious not to offend the new masters.

But two larger explanations are possible. First, Kaminski and the Latvians are merely the tip of a large and ugly iceberg, one that has itself been ignored for several years.

It's become bad form to mention it, because we are meant to be friendly towards the newest members of the European Union. But the truth is that several of these "emerging democracies" have reverted to a brand of ultra-nationalistic politics that would repel most voters in western Europe. It exists in Poland and Latvia, but also Lithuania, Estonia, Hungary, Romania and beyond. During the long decades of the Soviet era this chauvinistic, often racially supremacist politics was buried; but in 1989 it was exhumed, shook off the dirt, and breathed once more.

It shows itself in two ways. One is in a loathing for those deemed "other". Sometimes that's Roma people, often it's Jews. And this is not in the past, but the immediate present. Just this month Oszkar Molnar, an MP from Hungary's main opposition party – on course to form the country's next government – told a TV interviewer that "global capital – Jewish capital, if you like – wants to devour the entire world, especially Hungary". His party leader said there was no need to discipline him because he'd broken no rules.

But the more obvious manifestation of this old-new nationalism is its desire to rewrite recent history. Steadily, eastern European governments have sought to craft a new, internationally accepted narrative in which the crimes of Nazism and Stalinism are regarded as equal, with, if anything, the latter as the greater evil. It is the theory of the "double genocide", and it manifests itself in places like the Vilnius Museum of Genocide Victims which lingers on the 74,500 Lithuanians who suffered under Moscow rule but dedicates no exhibit to the 200,000 Jews murdered by their fellow Lithuanians in the 1940s. When the state prosecutor decided to chase up those guilty of war crimes from that period, he promptly investigated a quartet of Jewish survivors of the ghettoes who had escaped to fight the Nazis as partisans.

This is not the work of extremist parties on the lunatic fringe. The "International Commission for the Evaluation of the Crimes of the Nazi and Soviet Occupation Regimes in Lithuania" – whose very name implies moral equivalence and which omits the actions of Lithuanians themselves – sits inside the prime minister's office. The motive is not hard to fathom. These are ultra-nationalists who want to clean up their past, recasting themselves as victims – and forgetting the years in which their forebears were, in fact, the bloodiest perpetrators. Remember: the killing rate in the Baltics was among the highest in Europe; the percentage of Jews murdered was in the mid to high nineties.

Sadly, none of this really figured as we contemplated EU enlargement in 2004. We ushered in these new states without properly checking their baggage. They were pro-American and signed up for the "war on terror" and, for many on the right, that was good enough.

That blind eye has continued. In July, the Organisation for Security and Co-operation in Europe, which includes Britain, the US and Canada, issued a Vilnius declaration including much of this "double genocide" language. "The western mainstream has been tricked," says Prof Dovid Katz of Vilnius University, who after official pressure was forced to teach his truthful account of the Holocaust in students' homes this summer rather than on campus.

Which leaves that second explanation for our blindness. It's easy to imagine that the place of the Holocaust is almost sacred. It is taught in schools and has a national memorial day. It is, we imagine, a rare moral absolute in our secular age.

But that's in the abstract. When it becomes concrete, a real event committed by real people, suddenly we become hazy. "It was all a long time ago," the Tories say when confronted. "It was terribly complicated." Or, as Ken Clarke put it, airily brushing aside concerns about the party's EU chums: "It's all an anorak issue."

It seems we care about the Holocaust when we imagine it as an episode of historical science fiction, in which faceless "Nazis" belonging to no time and no place staged a terrifying horror show. But when anyone tries to anchor it in the real, to say that this happened in this place, with the enthusiastic participation of these people, polite company mumbles an excuse and shuffles for the exit.

Surely, by any moral standard, we cannot let this assault on historical truth stand. We owe at least that to the victims. If nothing more, it means demanding that the man set to be our prime minister ditch his friends in Europe – and find some new ones.

The strange thing is, I always knew that one day, when every last survivor was gone, there would be "debate" about the Holocaust. Claims that were once deemed shameful – questioning the veracity of documented events – would become somehow acceptable. But I never imagined that I would live to see that grim day for myself. Yet here it is: right here, right now.