For these reasons:why do you think they want war with Israel?
1) Israel is a bunch of Europeans and Russians who quite simply invaded an area that was multi-cultural (though strongly Moslem) for about 1500 years. To the locals, this is a (hopefully temporary) invasion and occupation of an area that already has residents.
Suddenly, following WWII, in come this tsunami of a minority culture who quite literally take the homes and villages of the locals at gunpoint (provided by the Brits at that time), despite the nonsensical PC propaganda we learn in the USA that the poor Israelis are the victims. They are not.
They are invaders from Europe and Russia who claim that their religion gives them the right to a home where someone else already lives.
They were VERY motivated invaders having just come out of WWII, Soviet brutality, and, of course, the Nazis. I can't really blame them for how that generation felt but it was wrong to inflict them upon an innocent population (the Palestinians). (The Jews should have been given their own state in the strongly Nazi areas. Punish the guilty, not an irrelevant third party.)
Many Muslims want to protect members of their own religion, so that's why they take this so personally.
Also, again, despite the white-washing of Israel's actions in the US media, the Israelis are brutal and humiliate and punish the locals they displaced in hopes that they will all get up and leave. Go read Likud party statements - don't trust me on this (and don't trust the American press).
2) The barbaric Middle Eastern despots keep their populations riled up against Israel in order to keep their anger focused elsewhere and prevent the kind of revolts that we're now seeing in Tunesia, Egypt, Lybia, Yemen, Bahrain, and perhaps Saudi Arabia, Jordan and Syria. (I'll bet $10 that Algeria will revolt within the next three years...)
3) The counter-force to these Middle Eastern despots is Islamism (a political movement based upon the religion). Al Quada started as a counter-force against these dictators and not against the West. Their ideology is one that unites Muslims against non-Muslims. Israel is obviously not Muslim and the fact that it is built upon 1,600 years of Muslim homes makes it easy to rally the Islamists against.
I'm not saying any of this is morally right or wrong, just that this is the mechanism and the set of beliefs that motivate the "they" in this question:
why do you think they want war with Israel?
(Personally, I think we should have followed FDR's policy toward the Middle East and never should have gotten involved in the region. Damn Truman for getting us mixed up in the Unholy Land. But that's all spilled milk at this point).