"They forbid rational speculation, and strive to kill their adversaries. This is why truth became thoroughly silenced and concealed."
Al Razi 854 CE
They are destroying the rich history and diversity of the East.
ISIS cannot tolerate Pluralism and historical diversity.
The Buddha statues blown up by the Taliban. The destruction and defacing of ancient Mesopotamian history. The war on Zoroastrian, Yazidi, Shiite, Sufi and Christian peoples in the East. They cannot tolerate the diversity of the present much less the diversity of the past. They cannot appreciate ancient Babylonian, Persian, Assyrian, Sumerian, Indian, Greek, and Egyptian culture because for them they are all pagans and ignorant polytheists.
As the great Muslim philospher Ibn Rushd stated,
"After logic we must proceed to philosophy proper...we have to learn from our predecessors, just as in Mathematics and Law. Thus it is wrong to forbid the study of ancient philosophy."
Ibn Sina stated "I devoted myself in studying the texts - the original and the commentaries - in the natural sciences and metaphysics, and the gates of knowledge began opening for me."
The ideology of ISIS has some roots in Salafi and Wahhabi teaching which pulls from a narrow fundamentalist version of Islam which cannot tolerate diversity either in ideas or history. There is an outright hostility and bigotry towards those that are deemed Infidels, Pagans, Polytheists, Apostates, Disbelievers, Kafir, Rafida. It is the bigotry against diversity and doubt. The hateful fear of the disbeliever. Apostophobia and Infidelophobia.
ISIS is a hate group that uses violence to further their goals not just rhetoric.