There was the Thugee Cult in India in the 18th Century. Remember how the British dealt with them? A model, perhaps, for the Islamist cancer.
The Crusades, The Inquisition...should I go on?
And not only that, but in the Bible, G_d himself killed everyone on the face of the Earth (except for Noah and his family) with the Deluge, as well as all the first-born children of Egypt in order to get the Israelites freed.