The essential message from Anders Behring Breivik’s mass murders in Norway is that it is foolish to rush to judgment about any crime and that Western democracies need adequately resourced intelligence services and police forces. There is a threat to the West from home-grown extreme right-wing groups, invariably of the neo-Nazi variety. And there is a threat from Islamists, both residents and visitors.

The Norway murders and Timothy McVeigh’s 1995 bombing of the Murrah Building in Oklahoma are examples of extreme right-wing terrorism. Breivik appears to have been a narcissistic loner but he had some links with the Knights Templar movement and the lunar right English Defence League. McVeigh had a relationship with the American militia movement, which is hostile to government.

However, the activities of the terrorist right should not be used as a cloak to diminish the real threat posed by Islamist terrorism – of the kind experienced in the US in 2001, Bali in 2002, Madrid in 2004, London in 2005 and Mumbai in 2008. Moreover, it would be unwise to assume that extreme left terrorism, of the kind that took place in North America and Western Europe in the late 1960s and the 1970s, will not be revived.

Some of the left-wing commentators who are now warning about the threat from the likes of Breivik are the very same people who railed against the governments led by Tony Blair in Britain, George W. Bush in the US and John Howard in Australia when they revamped anti-terrorist legislation and police powers in response to al-Qaeda’s attacks of a decade ago.

Last week, the New York Times ran a headline depicting Breivik as a ”Christian extremist” while other media outlets have labelled him a ”white extremist”. Breivik is certainly white – so much so that he is said to have undergone plastic surgery to look like an Aryan Nazi. But he does not belong to any Christian church and he has condemned both the Catholic and Protestant faiths.

To coincide with his killings, Breivik issued a 1516 page rambling manifesto titled ”A European Declaration of Independence”. This is a combination of white extremism, racist anti-Muslim sentiment and extreme environmentalism.

It is too early to judge whether or not Breivik is sane. Geir Lippestad, the accused’s lawyer, believes his client is insane. He has also described him as cold and without empathy – traits common to the lone psychopathic killer. Lippestad is a member of Norway’s Labour Party, the organisation targeted by Breivik.

In Australia, some left-wing commentators have focused on the fact that Breivik cited some well-known Australians in his manifesto – Peter Costello, John Howard, Cardinal George Pell, former Liberal MP Ross Cameron and historian Keith Windschuttle. It is easy to score ideological points against political opponents who have been cited with approval by a mass murderer. However, a reading of Breivik’s manifesto reveals that the Australians named have nothing to be defensive about.

Costello is quoted as declaring that Australian Muslim leaders should denounce terrorism and Howard is referred to as stating that Islamist migrants to Australia should adapt to Australian ways. Cardinal Pell is cited as expressing concern about invocations to violence in the Koran and about the deeply anti-Christian views held by some secularists. Cameron’s citation turns on his view that young men should commit to women and agree to have children. And Windschuttle is mentioned as someone who is disturbed about an anti-Western culture in many of our universities. That is all.

All of these comments are considered. None has provoked acts of violence in Australia.

One problem with the reaction by sections of the left to the Norway murders is that it is intolerant in itself. If the likes of Costello, Howard, Pell, Cameron and Windschuttle cannot say what they said, there would be no free debate at all.

There is room for a thoughtful discussion about Western culture, immigration and birth rates, which can readily co-exist with opposition to terrorism from the extreme right, the extreme left or militant Islamism.

An unpleasant tension currently exists in Australia – probably unmatched since the Great Depression in 1931 and the constitutional crisis in 1975.

In both those instances, the tension was resolved by political events that led to a general election. No such outcome is likely in the immediate future.

There is an obligation on all involved in the public debate to moderate their language, to desist from exaggeration and to disavow symbolic or real physical violence. However, mass murder in Norway should not be allowed to inhibit free speech. That would be counter-productive.

Gerard Henderson is the executive director of The Sydney Institute.