Political violence is generated based on shared fantasies about certain classes of people. Hitler had a fantasy about the Jew that led to the enactment of the Holocaust. Lenin had a fantasy about the capitalist, which led to tens-of-millions of dead people killed by Lenin and his disciples, Stalin and Mao and Pol Pot. 

Moslems possess a fantasy about "non-believers," which is the source of terrorism.

Those that are killed, somehow, threatens the beliefs of the believers. The non-believer negates the belief or fantasy or the believer, which menas the non-believer must be negated or crossed out.

Why do those who do not embrace one's own sacred object elicit such profound anxiety? People who root for the Boston Red Sox don't kill members of the Yankee team (although they may have the impulse to do so).

This is the fundamental question one must pose in the study of political violence? Why do those who do not believe in one's own sacred ideology evoke such rage?  Why do non-believers in one's own sacred ideology produce such profound anxiety--such that these non-believers must be wiped off the face of the earth.

Kill Jews, kill capitalists, kill the infidels. Each group has its favorite enemy. It's the same template. The same fantasy. In our hearts the dream remains the same. It happened in 1914 and its happening now. Historians write gigantic tomes (tombs) as if they are discovering something. However, as Yogi Berra understood,  it's simply "deja vu all over again." 

Richard Koenigsberg