I think this article is fundamentally wrong.
Islamists have not completely distorted the religion of Islam as we'd like to imagine (that would certainly make ourselves feel more PC and more armed to fight this threat), but are actually traditionalists in nature.
The assertion that Osama bin Laden primarily wants to bring America to its knees is false.
Osama writes and speaks from the same fundamental viewpoint as Mawdudi, Taymiyyah and ultimately Qutb. It is an internal, domestic struggle.
They want to first bring the Middle East under their control in order to establish a one world Ummah or Islamic state which is ruled by a "rightly-guided" Calipha (much like the Pope) with strict adherence to Sharia (Islamic law).
In order to achieve this vast plan of one world worshipping Allah, they feel the must first conquer the regimes of the Middle East that are apostates.
In this calculation, they see the West as the foremost supporter of these regimes. So in order to bring down the Middle Easter governments, the Islamists targeted the United States in an attempt to bring instability to these regimes.
Osama bin Laden calculated that the US was really a "paper tiger" in nature. He felt the US would violently lash back after 9-11 and create what Huntington would call "A Clash of Civilizations." He thought we would immediately invade Arab countries releasing a pandora's box and that, because our society is extremely casualty-averse (as seen currently in the war in Iraq), we'd fold after we had some losses. And after we folded in the Middle East, they could set up shop.
He calculated wrong.
The idea of socialism sparks some Islamists to action, but the gather their ideas more so from the Quran rather than the West.
The Quran squelches individualism and glorifies building a hudud (wall) around their society to keep everyone in as a collective body.
I would hardly attribute so much of their rational calculations as a result of postmodernism. That's letting them off the hook too easily.