Simply the belief in an epic drama in which you seeing yourself fighting "evil" for the salvation of mankind. Combine this with the willingness to do whatever it takes to achieve one's goal and a belief that the ends justifies the means and we have the conditions for a bloodbath.
Here is a link to an article by Kim Michaels on the subject of epic dramas.
"The epic struggle, once it has engaged you, quickly becomes a personal struggle that traps many spiritual seekers in fighting for what they think is a good or spiritual cause. In reality, the struggle is a complete illusion, or rather a drama, and it will never accomplish any spiritual purpose. It will keep you trapped in a downward spiral that feeds your spiritual light to forces that oppose God."
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