The timing, of course, was a major part of the problem, but also in a way unavoidable. It seemed completely crass for Cameron to make a speech focused on the threat of Islamist extremism on the day when the English Defence League was making its biggest ever anti-Muslim demonstration in Luton. But Cameron didn’t pick the timing of the Munich Security Conference and I’m not sure he should let a few thousand yobs in the EDL dictate what he says and when to other heads of state, and in any case I’m not sure it helps the debate about Islamism if the only people conducting it are the EDL, who deliberately conflate Islam and Islamism.

Cameron’s speech was actually rather careful in trying to define ‘Islamist extremism.’ He stated ‘We should be equally clear what we mean by this term, and we must distinguish it from Islam. Islam is a religion observed peacefully and devoutly by over a billion people. Islamist extremism is a political ideology supported by a minority. At the furthest end are those who back terrorism to promote their ultimate goal: an entire Islamist realm, governed by an interpretation of Sharia. Move along the spectrum, and you find people who may reject violence, but who accept various parts of the extremist worldview, including real hostility towards Western democracy and liberal values. It is vital that we make this distinction between religion on the one hand, and political ideology on the other. Time and again, people equate the two. They think whether someone is an extremist is dependent on how much they observe their religion. So, they talk about moderate Muslims as if all devout Muslims must be extremist. This is profoundly wrong. Someone can be a devout Muslim and not be an extremist. We need to be clear: Islamist extremism and Islam are not the same thing.’

He then went on to explain that even if the grievances which fuel terrorism: economic and social exclusion of Muslim communities in the west, Israel-Palestine, autocratic Middle Eastern regimes backed by the west, were dealt with, ‘there would still be this terrorism. I believe the root lies in the existence of this extremist ideology’.

Almost everything said in the first seven paragraphs of his speech could have been said by Tony Blair. In fact it probably has been. I agreed with it.

But you get to paragraph eight and it lapses into a very weird and paranoid Daily Mail view of what’s allegedly wrong with British society.

Apparently there is a ‘doctrine of state multiculturalism’ which has ‘encouraged different cultures to live separate lives, apart from each other and apart from the mainstream. We’ve failed to provide a vision of society to which they feel they want to belong. We’ve even tolerated these segregated communities behaving in ways that run completely counter to our values.’

What Cameron has described isn’t multiculturalism though. It is multiple separate and parallel cultures that don’t mix.

That’s a reality in some parts of the UK where housing tenure and the location of certain sorts of jobs have meant that one bit of a town is Muslim and another bit is white so the schools, shops and so on are effectively segregated and people can grow up not knowing people from the other community in their town.

But that was caused by accidents of economic geography. I don’t think that’s the ‘multiculturalism’ envisaged by any ‘doctrine of state multiculturalism’. If any part of Britain really deserves the title ‘multicultural’ it’s London, particularly boroughs like mine in Hackney. And here it works. My borough is approximately 50 per cent ethnic minority but no single minority is above about 12 per cent (the 50 per cent divides pretty evenly into black Caribbean, black African, Kurdish and Turkish, south Asian Muslim, and Chassidic Jewish). The different groups are mixed in together and coexist extremely harmoniously. Not perfectly, but it’s still pretty spectacular given the conflict in the world. There is no point trying to argue against this form of multiculturalism. It exists and is a reality of life for millions of Londoners – with children like my five-year-old son sharing a classroom with children of a dozen different ethnicities (and plenty of mixed-race kids from multicultural families) and from every faith and none.

Cameron’s take is actually a rather deterministic, almost Marxist one. He thinks people become terrorists because of the structure of the society they live in, but that doesn’t explain why the vast majority from the same faith and background don’t.

There’s an element of self-blame too. Jihadists exist not because they are bad people with bad ideas but because the 1960s and the Guardian and leftwing local authorities created them. This is just as stupid and pernicious as the excuses made that terrorism is all the Israelis’ or the Americans’ or Tony Blair’s fault.

Maybe the truth is more frightening. That some people are intrinsically evil and latch on to an evil ideology that gives them justifications for acts of terror. And other people are dupes of those leaders who provide their cannon fodder. The pattern was similar under the Nazis and Stalinists.

Cameron also gets terribly confused over Egypt. ‘We want to see the transition to a more broadly-based government’ he says. Great. But won’t any ‘more broadly-based government’ in Egypt inevitably include the Muslim Brotherhood, who are Islamists (whether of a violent or non-violent kind is disputed), ie. supporters of the ideology he has just attacked at some length (‘people who may reject violence, but who accept various parts of the extremist worldview, including real hostility towards western democracy and liberal values’).

I think Cameron may have been only a little less simplistic than the EDL in the definitions of Islamism he sets out (a violent kind and an anti-Western democracy and liberal ideas but non-violent kind). I’ve sat in a Mosque with Muslims I know well who told me proudly they were Islamists in a sense that Cameron doesn’t seem to have realised is possible. They were politically active members of mainstream British political parties, but see their participation in politics as an expression of their Islamic values. They supported and did not want to get rid of British democracy. While conservative and ultra-religious in the way they lived their home lives they were tolerant enough to accept the western lifestyles of the people around them. They were really hostile to the US, Israel and British foreign policy in a way I found pretty offensive (but so are most Guardian readers and quite a large slice of the PLP). They want a state based on Islamic values in their home country and other majority Muslim states but one with a democratic political system. In their home countries they would vote for Islamist parties.

I’m sure there are many Tory MPs who have Muslim activists in their local party associations with similar views. And I know from the contact I have with the Chassidic Jewish community in Stamford Hill that this sort of worldview has its exact miror image in that community – and that community would incidentally fall foul of Cameron’s concerns in his speech about women’s rights and separation versus integration, as would some fundamentalist Christian sects.

So Mr Cameron needs to be careful that by a blanket denunciation of Islamism he doesn’t alienate some quite moderate, responsible and civic-minded people who self-define using that phrase but represent no threat to democracy. Whether their values mean they all belong in mainstream parties is another matter, and another argument being tested in Tower Hamlets.

And I do wish he’d stop talking about liberal democracy being ‘western’. Doesn’t really explain the liberal democracies thriving in India and Japan. Liberal democracy is a universal human set of values not a western one.

There’s also the slight conundrum that our very good NATO allies in sort-of democratic Turkey have an Islamist government.

And another unaddressed conundrum – our staunchest ally and key trading partner in the Middle East – Saudi Arabia – fails every single one of Cameron’s tests (‘do they believe in universal human rights – including for women and people of other faiths? Do they believe in equality of all before the law? Do they believe in democracy and the right of people to elect their own government? Do they encourage integration or separation?’) and yet it is on the side of the west in the ‘War on Terror’.

And, as Egypt is showing, sometimes belief in democracy means accepting that people who don’t share our precise vision of western liberal democracy – Islamists, Communists, Sarah Palin and the Tea Party – are allowed to contest and win elections if that’s what people want to vote for.

I think what he meant to talk about is ‘violent extremist Islamists’ and ‘non-violent extremist Islamists’ and to then contrast these two groups with ‘moderate Islamists’ and ‘Muslims who are not Islamist at all’. For me the dividing line is support for pluralism and ongoing elections rather than a ‘one election then we’re in for ever’ ideology.

But it’s a complex subject that he’s gone blundering into, and I’ve probably committed equal offence by blundering in with this article.

I was back with him on his conclusions. Confronting extremist ideology. Banning hate preaching. Proscribing organisations that incite terror. Not chucking money at or sticking ministers on platforms with non-violent extremists. Stopping extremists recruiting in colleges and prisons. Agreed on every point.

And I agreed that ‘a genuinely liberal country does much more; it believes in certain values and actively promotes them. Freedom of speech, freedom of worship, democracy, the rule of law, equal rights regardless of race, sex or sexuality.’ But I’d add another value that a ‘genuinely liberal society’ should promote: multiculturalism. Not blind moral relativism that says all sets of values are equal and that cultural norms that for instance oppress women should be tolerated, but a true multiculturalism that says these little enclaves like Hackney where cultures coexist in peace show the best hope for a future without war. It’s sad that Cameron took a swipe at multiculturalism when it is the antithesis of what the hate-mongers, be they in the BNP, the EDL or al-Qaida, believe in.

Photo: Paul Galipeau