Religious fanaticism
Historically, the term was applied in Christian antiquity to denigrate non-Christian religions, and subsequently acquired its current usage with the Age of Enlightenment.
[1] Lloyd Steffen cites several features associated with religious fanaticism or extremism: Ever since Christianity was established, some of those in authority have sought to expand and control the church, often through the fanatical use of force.
[6] An example of Christians who didn't line up with Orthodox ideology is the Donatists, who "refused to accept repentant clergy who had formerly given way to apostasy when persecuted".
Charles Selengut, in his book Sacred Fury: Understanding Religious Violence, said: The Crusades were very much holy wars waged to maintain Christianity's theological and social control.
On their way to conquering the Holy Land from the Muslims by force of arms, the crusaders destroyed dozens of Jewish communities and killed thousands because the Jews would not accept the Christian faith.
The inquisitors generally saw themselves as educators helping people maintain correct beliefs by pointing out errors in knowledge and judgment...
[11] From their essentially political position, the Kharijites developed extreme doctrines that set them apart from both mainstream Sunnī and Shīʿa Muslims.
[11] Shīʿas believe ʿAlī ibn Abī Ṭālib is the true successor to Muhammad, while Sunnīs consider Abu Bakr to hold that position.
[11][12][13] Sayyid Qutb, an Egyptian Islamist ideologue and prominent figurehead of the Muslim Brotherhood in Egypt, was influential in promoting the Pan-Islamist ideology in the 1960s.
Thomas Farr, in an essay titled Islam's Way to Freedom, states that "Even though most Muslims reject violence, the extremists' use of sacred texts lends their actions authenticity and recruiting power".
According to Ellens, the al-Qaeda members who took part in the terrorist attacks did so out of their belief that, by doing it, they would "enact a devastating blow against the evil of secularized and non-Muslim America.
