Let me put it another way
A general does not necessarily tell his men all the details, he gives them their orders. If they knew they were going into a suicide mission, for instance, they may be less likely to sacrifice themselves. Their perspective on the battlefield is intentionally left as narrow as possible to ensure they follow their orders to the letter and don't jeopardize the greater conflict being waged in self-interest. The soldiers can only have faith in their country to lean on, not knowledge of the details.
Perhaps the sacrifices the terrorists are making are necessary to stop Western Powers from enslaving us all. The fact is, none of us know the future. We can use principles to guide us through the present but these principles also hinge on our unique perspectives. We can figure out the best way to act based on the way we see things, but we cannot figure out the best way to act.
Truth is only relevant in action, anyways.