FTA:

Ideology—that is what gives evildoing its long-sought justification and gives the evildoer the necessary steadfastness and determination. That is the social theory which helps to make his acts seem good instead of bad in his own and others’ eyes, so that he won’t hear reproaches and curses but will receive praise and honors. That is how the agents of the Inquisition fortified their wills: by invoking Christianity; the conquerors of foreign lands, by extolling the grandeur of their Motherland; the colonizers, civilization; the Nazis, by race; the Jacobins (early and late), by equality, brotherhood and the happiness of future generations.

He could have added, “…jihadists, by the glory of a new Caliphate.”