Righteousness and patience
"It is not righteousness that you turn your faces East or West; but it is righteousness - to believe in Allah and the Last Day, and the Angels, and the Book, and the Messengers; to spend of your substance, out of love for Him, for your kin, for orphans, for the needy, for the wayfarer, for those who ask, and for ransom of slaves; to be steadfast in prayer, and practice regular charity; to fulfill the contracts which you have made; and to be firm and patient, in pain (or suffering) and adversity and throughout all periods of panic. Such are the people of truth, those who fear Allah" [Qur'an 2:177]
As I read this, I thought about how the terrorists could be interpreting this. It seems to me that it says that good Muslims should be good people and strive to overcome whatever obstacles they find in their path. I don't see any incitement to kill anyone here, in fact it seems to be saying to "turn the other cheek".