Has anyone noticed that a lot of the people who refuse to blame Islam for Muslim terrorism are more than willing to blame Christianity for the crusades and the witch hunts?
A religion is defined by its founders. If its caretakers violate the original creed, those violations cannot be considered part of that creed. Otherwise one reading the Old Testament would have to conclude that Judaism changed from time to time with regard to tolerating idolatry. The Law of Moses never changed; certain Hebrew monarchs simply chose to disobey.
Christians were never
given the political authority granted to ancient Israel (see my 2003 post The Bible, Theocracy, And Troublesome Laws
), and not even theocratic Israel was empowered to prosecute general heresy. Also, the medieval methods for identifying witches are not in the Bible.
A thorough accounting of the Koran's statements on just and unjust war would settle the issue on Islam's views on various terrorist practices.