nice piece, but the analogy has its weaknesses
1) the Islamists aren't dumb rocks following Newtonian paths in space with no will of their own - they are (for better or worse) sentient beings with ideas and intentions;
2) unlike the asteroid, they really do want to "get" us - even if Dubya had never existed.
Apart from those tiny major quibbles, that was an entertaining polemic .. of course, I get the point you were trying to make.