Timothy Garton-Ash writing in today’s Guardian makes a characteristically robust defence of free speech in the wake of Anders Breivik’s massacre in Norway, in which he addresses the ever-present call for online censorship whenever an extremist is found to have been motivated, even in the slightest sense, by findings on the web.

In an age of less organised politics, the question is what exactly would one ban? Breivik is not a Nazi, though there are elements of fascist thought in his nativism and conspiracist paranoia. Indeed, members of the traditional far right were quick to distance themselves from him — British National Party leader Nick Griffin tweeted “The Oslo mass murderer is not a nationalist but a free market liberal, anti-Muslim Zionist”. So banning the “traditional” far right would not miss the point.

The worrying thing about Breivik is that his ideology is based on some very, very mainstream ideas. Grievances about “political correctness”, the “feminisation” of society, single parent families and the Islamisation of Europe are widespread. They fuel Geert Wilders Party for Freedom in the Netherlands, and in France, Marine Le Pen is leading the Front Nationale towards this populist ideology — distinct from her father Jean Marie’s more straightforward fascism.

Garton-Ash quotes Bruce Bawer, a writer quoted frequently quoted in Breivik’s manifesto. Writing in the Wall Street Journal, Bawer noted: “Breivik quotes approvingly and at length from my work, mentioning my name 22 times. It is chilling to think that blog entries that I composed in my home in west Oslo over the past couple of years were being read and copied out by this future mass-murderer in his home in west Oslo.”

So here’s a reasonably mainstream writer — a man whose books are published by Doubleday and whose articles are published in the Wall Street Journal, whose ideas are appropriated by someone to justify his own means and ends.

I was a little surprised to find my own work (it was this article on blasphemy laws) quoted approvingly in Bruce Bawer’s last book Surrender: Appeasing Islam, Sacrificing Freedom. Despite having been a vocal secularist pretty much my entire working life, I disagree strongly with the conflation of “Islam” the religion and “Islamism” the political ideology that the title and some of Bawer’s works suggest.

But this is how ideas work. Once we put them out there, we relinquish ownership. I cannot tell Bawer not to read and cite my work, anymore than Bawer could have told Breivik not to read his. Did Bruce Bawer, or Melanie Philips, or Jeremy Clarkson make Anders Breivik do what he did? No. Of course not. Did their ideas influence his? Yes. Of course.