The aesthetics of evil in Islamic fascism using IS as an example

The question is if evil does not 'fall from the sky' if it is not God-given why are IS supporters so brutal? They are either truly insane or we need to understand and define them differently. If they were insane they would be untamed wild animals according to Schopenhauer. We should not morally condemn them. What IS does is in line with its religious beliefs. Its followers believe in God and call their actions 'God's will'. Thus with their brutality they believe they are following the command of their God. However there is no clear passage in the Koran that allows Muslims or believers to kill and torture in the name of God. IS operates within the framework of this morality in its religious view. This does not fit in with common Islamic Christian atheist and other concepts of morality. There are many IS assassins who still consciously or unconsciously dream of paradise and are fighting against their enemies to achieve it just like other religious extremists before them.