People do not blow up buildings, crash airliners, and wreck passenger trains because they want to be left alone. They do these things because they want to be feared, or barring that, paid attention to.
Meaning what? Stop satellite broadcasts of Baywatch? Stop consuming oil? Change our minds about Israel's right to exist? Decide that honor killing isn't so bad?
Al Qaeda have already shown they are cynical enough to employ teenagers as suicide bombers, mosques as headquarters, hospitals as munitions dumps. Waging war against the Great Satan makes them a headline act on the global stage. They've probably even figured out a way to get paid for it. Isn't it possible that the Al Qaeda leadership -- who let others take on the suicide missions -- just like this state of affairs?
Is it so hard to believe that their narrative of grievance and justification is self-serving, and exists primarily to help them recruit more ammunition?
In the New Testament (Christianity) there isn't a clear cut statement about killing the unbeliever. There is Matthew 1:34, "Think not that I am come to send peace on earth: I came not to send peace, but a sword" and Luke 22:36, "Then said he unto them, But now, he that hath a purse, let him take it, and likewise his scrip: and he that hath no sword, let him sell his garment, and buy one" but no direct commandment to otherwise kill the unbeliever.
In the Koran, I found three passages that directly state the killing of unbelievers (translation by Mohammad Habib Shakir):
2.191 And kill them wherever you find them, and drive them out from whence they drove you out, and persecution is severer than slaughter, and do not fight with them at the Sacred Mosque until they fight with you in it, but if they do fight you, then slay them; such is the recompense of the unbelievers.
4.98 They desire that you should disbelieve as they have disbelieved, so that you might be (all) alike; therefore take not from among them friends until they fly (their homes) in Allah's way; but if they turn back, then seize them and kill them wherever you find them, and take not from among them a friend or a helper.
4.91 You will find others who desire that they should be safe from you and secure from their own people; as often as they are sent back to the mischief they get thrown into it headlong; therefore if they do not withdraw from you, and (do not) offer you peace and restrain their hands, then seize them and kill them wherever you find them; and against these We have given you a clear authority.
And one passage about killing those that wage war against Islam:
5.33 The punishment of those who wage war against Allah and His messenger and strive to make mischief in the land is only this, that they should be murdered or crucified or their hands and their feet should be cut off on opposite sides or they should be imprisoned; this shall be as a disgrace for them in this world, and in the hereafter they shall have a grievous chastisement,
I only looked for passages that directly stated it was okay to kill unbelievers; I did not look for mor subtle passages that implied such. If you think I'm being unfair here, please point out any other passages from The Old Testament or New Testament that I may have missed.
That being said, more terrorists are probably motivated by meddling or foreign troops on their soil than what is written in the Koran, so I'm guessing it's more like adding fuel to the fire than the root cause.
Perhaps you are not aware of this, but Judaism's "canonical" text is not the Torah but the Talmud. Talmud is not equivocal regarding the nature (and constraints) on relations with the non-Jew ("Goyim") and its instructions are not dead-letters but accepted to this day.
The Crusades are an off-mentioned bugbear on the lips of moral relativists, and of course the Bible claims that the Hebrews drove out pagan tribes from the land of Cainaan. But in my opinion we ought to weight recent killings in the name of God slightly higher than those which occurred five hundred or three thousand years ago.
I could be wrong and biased because of the media I consume. Could you point me to a recent news story about a Christian or Jewish suicide bomber?
I mean, think about this: the poor terrorists-that-we-call-terrorists blow themselves up ... and we don't even listen to their message. (Which is usually "hey, leave us alone pls, kthnxboom") Then some yokel gets his 15 minutes to tell us how we need to spend billions on something he's getting kickbacks for. Who here is using terror more effectively?
Once the public has realized that there is (statistically) no root-cause terrorism, we can have appropriately relaxed security once again. And more money.