Short answer: They're "Wahabbi terrorists."
Is it fair to call the hijackers "monotheist terrorists"? They are monotheists, as they believe that there is no God but God. Strictly speaking, they are monotheist terrorists. Here in the States, we have our own monotheist terrorists. Iran sponsors "Hezbollah," the "Party of God." Meanwhile, the US has an "Army of God," which attacks abortion clinics and doctors.
But the media call the hijackers "Muslim terrorists," not "monotheist terrorists." The implication is that it's the terrorists' particular branch of monotheism, Islam, that best describes them. The term implies that the Muslim branch of monotheism is different from the "friendlier" branches (Christianity and Judaism). Non-Muslim monotheists would say that it's not fair to brand all monotheists as terrorists with the term "monotheist terrorists."
Of course, Muslims say it's not fair to brand all Muslims as terrorists with the term "Muslim terrorist," but there you go.
The question becomes, "Does the phrase 'monotheist terrorist' better describe the terrorist than 'Muslim terrorist'?" Were their crimes committed because of some quality of Islam? Or is it a quality of monotheism in general? Does the sense of moral superiority that follows so often from monotheism make it easier for monotheists to kill thousands of their spiritual enemies? Does the implicit message of "us (God's true believers) vs. them (the devil's children)" make it easier for monotheists to plan wanton destruction, provided that destruction is directed against outsiders? Does the idea of "one God" lead too often to "one way to God," and from there to "destroy the infidels"?
Maybe, maybe not.
Maybe it's not monotheism at all that creates the potential to believe that mass slaughter is a holy act. Maybe it's just religion in general. Would the attackers be better termed "religious terrorists?" Is it monotheism in particular that made them dangerous, or is religious fervor in general the culprit here?
Or is the hijackers' act of terror just another example of people committing atrocities against other people? Maybe the ethnic and religious elements of the conflict are just surface details, and the attacks are really about nationality, wealth, and power.
Maybe, instead of looking for a broader adjective than "Muslim," we should look for a more precise one. The terrorists belong to a particular branch of Islam: Wahhabism. Wahhabis are anti-modern fundamentalists who support the Saud royal family as God's rightful rulers on earth. Not surprisingly, the Saud royal family scratches the Wahhabi's backs in returrn. That's why the Saudis spent so much money supporting extremist Wahhabi schools in Pakistan.
The term "Wahhabi terrorist" is fair and informative. Not all Wahhabi's are terrorists, but they're extremists, and lots of them are indeed terrorists.
Perhaps the media shy away from calling the terrorists Wahhabis because that label would make clear the relation between the corrupt Saud royal family (our putative allies) and the terrorist attacks on the US.
Christian Tribe: More on monotheists and infidels.