The United Nations. I wish I was kidding. A huge part of the problem is that the UN peacekeepers run schools to help educate Palestinians, and the education is, well... not sure how long this will stay available, YouTube likes deleting accounts that broadcast these kinds of things.
This whole video can be enlightening but the part about education begins at about 0:50. "Neutral" UN teachers have their first-grade students chant "Palestine is an Arab land from the river to the sea" the way an American class might have the kids chanting "remember to say please and thank you" while teaching manners, then goes on to teach the kids "The Jew is the wolf" and other slurs. It goes in depth into the matter from there.
I'm of the opinion that this is actually one of, possibly the biggest obstacle to peace. The Palestinians act like complete boneheads and keep performing attacks that can't possibly succeed because they've been taught to do so, by the UN, since they were in the first grade and that kind of deep childhood indoctrination is really hard to throw off. Somebody cleaning out the educational system wouldn't fix all the deep systemic issues but in a generation it could produce people willing to actually talk and negotiate.