The Origins of 9-11
Edmund Standing has a very interesting and informative post on the background that led to Al Qaeda and 9-11.
It is precisely this narrow definition of 'legitimate targets' that led to al-Qa'eda moving from terrorist attacks on Arab governments supportive of the West to attacks on Western troops and officials in 'Muslim countries', and finally to terrorist attacks against civilian targets in America on 9/11. The kind of idiotic claims made by 9/11 troofers about there being 'no reason' to think that followers of bin Laden and Zawahiri would have carried out 9/11 ignores this evolution into advocating direct attacks on Westerners that occurred in the '90s.
It is apparent to me that very few "Truthers" have read anything on the backgrounds of militant Islam. This is an excellent, if abbreviated version; if you want the full thing, I recommend the Looming Tower.