Extremism exists in every major faith, and sometimes turns violent
The focus for the most groups has been making Islam more of a presence in the secular world. They have held Islamic study camps, where people study the Quran, pray, and renew themselves spiritually. The ultra-Orthodox Jewish fundamentalists devote their attention to studying Torah and Talmud and preserving true values in a Godless world. Sometimes in Israel they may stone the cars of Israelis who ignoring the Sabbath rules or attack one of their own number whose behavior seems lax. But in general, they are not violent. And the vast majority of American Protestant fundamentalists, as I said above, do not commit acts of violence: they confine their "battle for God" to amending text books, which teach evolution or liberal values, or for school prayer.
What responsibility does Islam bear for these acts? What does the Qu'ran say about violence?
The word Islam, which means "surrender," is related to the Arabic salam, "peace." When the Prophet Muhammad brought the revealed scripture called the Qu'ran ("recitation") to the Arabs in the early 7th century C.E., one of his main purposes was precisely to stop the kind of indiscriminate killing we saw on September 11th.
At the time the Arabian Peninsula was in crisis. The tribal system was breaking down, and the various tribes were locked into a murderous cycle of vendetta and counter vendetta. For a weak tribe, or a man who lacked powerful protection, survival was nearly impossible. The Prophet himself suffered several assassination attempts, and when his religious and social message ran him afoul of the establishment of Mecca, the small Muslim community was persecuted. Things got so bad that the Muslims had to migrate to Medina, some 250 miles to the north, and there they were subject to attack by the Meccan army, the greatest power in Arabia.