Depending on the timeframe and how narrow you focus on the violence, anyone of the above mentioned individuals or organizations could be at fault. The Bible and Koran are clear on that point, but disagree over who was to be sacrificed at the altar by Abraham to show his loyalty and devotion to God. Jews believe that Isaac was the one saved while Moslems believe it was Ishmael. Of course, people tend to look to more recent events - namely the Sharon visit to the Temple Mount or Arafat's reluctance to issue public statements calling for the violence to end. Those situations, plus the near daily attacks in a tit for tat fashion, exascerbate the situation to the point where noone really cares why things started or want things to end.
Revenge becomes the name of the game.
Revenge is a dangerous game in international relations and interpersonal relationships. You have two communities that are inexorably tied together by geography and politics and neither side really accepts the other's rights in even the most basic ways. Those in charge haven't gotten past the rhetoric to deal with the basic communication issues and to deal with the grief and bloodshed that has wrapped the Israelis and Palestinians together in a death grip. Used under License.