One of the peculiarities of intellectual history is its effect as a distorting lens of the facts. Someone who misunderstood something is used as a source by another, and pretty soon discussions have no basis in reality and only serve to buttress prejudices.

I enjoy occasional polemics and links from samizdata.net but this article, The Western Roots of Islamism is riddled with so many half-truths and distortions that one is inclined to dismiss its entire thesis; and I believe that Islamism, the modern form of Islamic supremacism, is based on western thought.

So let us Fisk it. Notebooks out pseuds!

to understand Osama Bin Laden we ought to remind ourselves of the work of Heidegger

I would recommend actually reading something about Heidegger, say an encyclopedia article, before "reminding" oneself in a vacuum.

Heidegger may have "inspired several generations of European leftists", but only in the sense that he "inspired" thinkers on the left, right, middle, east, and west; i.e. he's the most cited XXth century philosopher in the philosophical literature of the XXth century. A quick search of Heidegger and Marx on Google would have revealed that Marxists tend to disagree vehemently with Heidegger.

Heidegger is part of a tradition of nihilistic romanticism

Now Heidegger had a soft spot for Hölderlin, they're both from the valleys of the upper Danube, and he sent romantic letters to Hannah Arendt. However calling Heidegger as a romantic is a common shibboleth often repeated in the Anglo criticism of him, but where is the actual romanticism in Heidegger? Dozens of his lectures have now been translated in English. How about some citations?

Heidegger was not a nihilist. He's the one that identified and criticized the nihilism inherent in Western philosophy starting from the Greeks. Plato idealism introduced nihilism through his idealism. Aristole weighs the arguments of the pre-socratics and Plato, and after that nihilism is locked into the foundations of philosophy.

[T]hat can be traced via Nietzsche and Marx and Fichte all the way back to Rousseau.

And a crooked via that would be. Marx and Fichte are Hegelians. Nietzsche and Heidegger are anti-Hegelians. Rousseau barely appears in their writings as an aside. They both trace their way of thinking back to the Greeks. Read Nietzsche's Birth of Tragedy, Philosophy in the Tragic Age of the Greeks, or the recently translated The Pre-Platonic Philosophers.

A key theme is the total destruction of existing bourgeois
societies and their replacement by a new authentic social order.

Really? Can a single citation be provided for this thesis? Heidegger was a family man that enjoyed living with country folk. Nietzsche was snob that wrote for other intellectuals. Where are their theses on social engineering?

Heidegger influenced French post-war Left apologists for Stalin and Mao such as Sartre,

This is a reiteration of the earlier logical fallacy; Heidegger influenced everyone that came after him, whether in a positive or negative sense. Sartre was influenced to write Being and Nothingness in the early 40s. When French officers occupying Heidegger's part of Germany brought Sartre to his attention, he responded with Letter On Humanism, repudiating Sartre's book; pointing out that it was Cartesian and hence a misinterpretation of Heidegger's own Being and Time. Later Sartre drifted into Hegelianism and Marxism, writing the Critique of Dialectical Reason, which can't even claim to be misinspired by Heidegger.

and via the Algerian writer Frantz Fanon

And where in Fanon's texts is Heidegger discussed?

Inspired by Fanon, such figures as Lin Piao,

Apparently inspired by a book written in 1961, Lin Biao got into a time machine and set about defeating Chiang Kai-shek's armies in 1947.

Gotta go. The kids are shrieking for breakfast.  ¶ 8:56 AM