Kenan Malik remembers the beginning. He was in Bradford to interview Sher Azam, president of the Bradford Council of Mosques and the guy who burned The Satanic Verses at a demonstration, and he encountered an old friend.

“I’ve been up here a few months, helping in the campaign to silence the blasphemer…No need to look so shocked. I’ve had it with the white left. I’d lost my sense of who I was and where I came from. So I came back to Bradford to rediscover it. We need to defend our dignity as Muslims, to defend our values and beliefs, and not allow anyone – ”racist or Rushdie” – to trample over them.” I was astonished. The Hassan I knew in London had been a member of the Socialist Workers party (as had I for a while). Apart from Trotskyism, his indulgences were sex, Southern Comfort and watching Arsenal. We had marched together, chucked bricks at the National Front together, been arrested together. I had never detected a religious bone in his body. But here he was in Bradford, an errand boy to the mullahs, inspired by book-burners.

An errand boy to the mullahs – there it is. Imagine what that would be like. Imagine you’re in Lynchburg or Boulder or Pocatello to interview Fallwell or Dobson about whatever the latest religiofascist move is – blaming feminism for September 11, for instance – and you encounter an old friend, a wine-drinking lefty – who turns out to be there not to mock, not to investigate but as an adherent. As an errand-person to the bible-bashers.

I transpose the terms because it’s obvious how disconcerting that would be to most first world lefties. But when it’s running errands for the mullahs rather than the bible-bashers, somehow the disconcerting quality is less obvious. There’s a tendency to confuse Islamists with freedom fighters instead of with Falwell-types. That is such a mistake…

Today, “radical” in an Islamic context means someone who espouses a fundamentalist theology. Twenty years ago it meant a secularist who challenged the power of the mosques. The expunging of that radical secularist tradition has played an important part in the rise of Islamic militancy in this country. Hassan embodied this mutation from left-wing activist to Islamic militant. He was not alone.

Just so. The expunging of that radical secularist tradition, and the replacement of it with its own opposite. It’s a horrible tragedy, and all the more so because it’s so confusing. There really are a lot of lost-in-the-fog types – including Guardian editors, apparently – who hear the words ‘radical’ and ‘militant’ and ‘activist’ and think they mean exactly what they did thirty and forty years ago – who simply haven’t grasped yet that they mean not exactly what they did, and not even more or less the same kind of thing with some inevitable modifications over time, but rather, the deadly enemy of the original meaning.

The Rushdie affair made me question my own relationship to the left. For the transformation of Hassan mirrored a wider political shift. It was a conversion from a belief in secular universalism to the defence of ethnic particularism and group rights. At one time, the left had been a champion of Enlightenment rationalism, of a common humanity and universal rights. Over the past 20 years, however, many key figures and organisations on the British left have promoted the idea of multiculturalism. “You have to treat people differently to treat them equally,” Lee Jasper, race adviser to Ken Livingstone, says. Or as Labour MP Keith Vaz put it, “Britishness cannot be imposed on people of different races, cultures and religions.” After Rushdie, I came to realise that tackling this “politics of difference” was as important as challenging racism…The roots of the politics of difference can be found in the new forms of radicalism that emerged in the 1960s. Radicalism came to mean the rejection of all that is “western” in the name of marginality or difference.

And the Other – don’t forget the Other, whatever you do.

Multiculturalism did not create militant Islam, but it created a space for it within British Muslim communities that had not existed before. It fostered a more tribal nation, undermined progressive trends within the Muslim communities and strengthened the hand of conservative religious leaders. It is true that since 9/11 and particularly since 7/7 there has been growing questioning of the consequences of multiculturalism. From David Blunkett to CRE chief Trevor Phillips, many have talked of the need to reassert common values. Yet the fundamental tenets of the politics of difference remain largely unquestioned. The idea that society consists of a variety of distinct cultures, that all these cultures should be respected and preserved and that society should be organised to meet the distinct needs of different cultures – these continue to be regarded as the hallmarks of a progressive, anti-racist outlook. The lesson of the past two decades, however, is this: a left that espouses multiculturalism makes itself redundant.

It undermined progressive trends within the Muslim communities and strengthened the hand of conservative religious leaders – didn’t it just. So we hear a great deal from Iqbal Sacranie in the Guardian and on the BBC and nothing from Maryam Namazie and Azam Kamguian. So much for radicalism.