A second reason I am against the clash of civilisations thesis is hinted at here, that political Islam is a product of the West and of modernity, not some atavistic, medieval anachronism. Courtney, of Neo-Jacobin, makes this point very well in a comment on the excellent ModernityBlog:
Generally, the rule for suicide bombers is 1) be born in the West, 2) be educated in the West, 3) convert to Islam in the West, 4) lash out at a powerful symbol of the West (US and UK soldiers will do quite nicely), and 5) have no ideological commitment to any other political position.
There are some noticable exceptions to the notion of masculinity, I'm thinking about the 38-year-old Belgian female by the name of Muriel Degauque, who was raised in the industrial town of Charleroi. She entered the history books as the worlds first white female suicide bomber. Muriel did try to kill American soldiers in Bagdad, but, thankfully, only managed to blow herself up to pieces.
Muriel conforms to my idea of what contemporary Islamic terrorism is all about. Often it's disaffected Western, or Westernised individuals who nihilistically lash out against something they hate, whether it's Bush, Blair, UK/US military, or Western societies and it's secular peoples in general.