Leading article: A massacre born from a poisonous mindset

A picture of almost unbearable horror has emerged from Norway. Reports of the systematic murder of young activists on the tiny island of Utoeya, lured to their death by a man dressed in a police officer's uniform, are as harrowing as those that followed the 1996 Dunblane massacre here in Britain.

Anders Behring Breivik, a 32-year-old Norwegian, is being held by the authorities under suspicion of carrying out the killings, as well as planting a car bomb in Oslo city centre last Friday. The signs are that Breivik is a maniac, intoxicated by the propaganda and paranoia of the racist far right. This is a timely reminder that political violence is not the exclusive preserve of militant Islamists. Indeed, there is a possibility that the intelligence services have lifted their eyes from the threat from the neo-Nazi right in recent years as militant Islam has dominated the headlines.

That would represent a dangerous oversight. Across Europe, the far right has been growing in strength in recent years, propelled by a strong current of Islamophobia. This poisonous mindset is sometimes stoked by ostensibly respectable political groups like Geert Wilders' Freedom Party in Holland, or mainstream voices like the former Bundesbank member, Thilo Sarrazin, who has written a best-seller called Germany Does Away With Itself.

Yet it has to be conceded that, from what we have learned of Breivik so far, it is hard to see how the Norwegian authorities could have picked him up before he went on his killing spree. He had no criminal record. He appears to have acted alone. There is, as yet, nothing that has come to light about his behaviour to suggest that the authorities were remiss in not apprehending him sooner.

This is a national trauma for Norway. The nation has suffered its greatest loss of life in a single incident since the Second World War. The Labour Party activists on Utoeya were drawn from all around Norway. Communities everywhere have been affected by the tragedy. The prime minister, Jens Stoltenberg, pledged at the weekend that Norway will not turn in on itself. He told a press conference in the hours after the tragedy that "we must show that our open society can pass this test too, that the answer to violence is even more democracy and that its traditions of openness and tolerance will be preserved." That is a laudable response. It would compound the nightmare if Norway were now to become a paranoid state, obsessed with security.

The test of the strength of any society lies in how it responds to shocks such as these. The Norwegian Muslim community's strong show of solidarity with all the victims of this outrage over the weekend is an inspiring repudiation of the nativist hate-mongering that Breivik is reported to stand for.

If any good can be dredged from the depths of this disaster, it will be a widening recognition that hate and intolerance, not Muslim immigrants, are the true enemies of European culture. The main purpose of all political violence – whatever end of the spectrum it arises from – is to divide. The best possible response from any society that suffers under this scourge is to refuse to be divided.