I don't think that the religion is the issue, I think that desperate people with desperate lives will always find something irrational to fill their life with and kill for.

As an example on a smaller scale (smaller as in less desperate) in Italy we have people whose life revolves around going to the stadium on Sunday to watch their football team and getting into fights with the fans of the opponent team. That's the only thing that keeps their life together. And they are ready to kill other teams' fans, we have people killed every year.

Likewise we have extreme right or extreme left groups who fight and kill each other... desperate people filling their life.

Religion, political faith, football team, doesn't really matter, the issue is the people, not the ideas.