"....As a pure aside I have a lot of sympathy for the Palestinian position, I mean, if I lived somewhere and a bunch of people turned up and claimed that 2000 or so years ago God gave them my country I would be a tad hacked off myself...." So which "Palestinian" people would that be? There is no such racial group as "Palestinians", there has never been a country called "Palestine", it was a moniker given to an area by the occupying Romans who were intent on breaking up the then Jewish kingdom. In the old days prior to WW1, even Jews that left the area referred to themselves as Jewish Palestinians. Old Saint George was more than likely a Christian Palestinian. The area covered by the Manadate under British control between WW1 and WW2 range as far as Iraq (another artificial, colonial, boundary creation) and included a number of ethnic groups including several Jewish tribes, Bedouin, Syrians Arabs, Christian Arabs, Christian Maronites and the Druze. Historically, the land of Israel has changed hands many times (Egyptian, Babylonian, Turkish, Jewish, Roman and Persian dynasties have conquered it at one time or another), so who is the "rightful" owner? The Muslim "Palestinian" Arabs you sympathise with (out of historical ignorance, it seems) were themselves invaders from the Saudi area. So, if you're willing to accept one people's claim simply by right of historical conquest then you can't argue if the Christians go on another crusade or the Israelis conquer all of the West Bank and claim back all of their old kingdom. Of course, if the "Palestinians" had just accepted the original UN partition plan back in 1947 then they would have had a state called Palestine and would probably be a lot better of right now, but I'm sure you wouldn't criticise them for throwing away that chance and every one since to negotiate a Palestinain state.
"....Why don’t the church’s, mosques, synagogues etc just excommunicate (or the religious equivalent) anybody who is involved with any act of violence...." In the case of Islam, there is no such concept as excommunication. Even if you are condemned to the Msulim equivalent of Hell you do so as a condemned Muslim. To leave Islam is a crime against Allah punishable by death, even in so-called moderate Muslim countries like Egypt. Just Yahoogle for Abdul Rahman in Afghanistan for an insight into what leaving Islam can entail.