"The only good Muslim is a bad Muslim" -- the ones who are pious and true to their faith do not condemn the goals of the terrorists, because they are the selfsame goals of their prophet as attested to in their Koran. The terrorists may be a minority of the total, but they are only a minority to the extent that they're willing to actually strap on the suicide vests themselves. The majority support them and provide aid and comfort. Have you ever heard an unqualified condemnation of them from a prominent Muslim or clerical authority? I have not. Their condemnations, when they are forthcoming at all, are usually of the "they shouldn't spook the prey like that; we think we should be nicer about it, but we're still going to overtake your civilization" form.
And LadyVirginia is exactly right about the supposed historical grievance vis-a-vis the Crusades. I will note that the Muslims were launching their own "crusades" into Europe and North Africa centuries before the first European Crusade into the Holy Land. What were they seeking "revenge" for at Tours?