I'm not a fucking encyclopedia
I suppose that they were regarded as different or foreing because they didn't assimilate with locals. So people would have bad opinioon about them as we usually have about things or people we don't know or understand. I presume that is how the stereotypes are being developed.
BTW no wonder Arabs are trying to get rid of Isreal, they consider you as invaders. They have god dammn good reason to hate you. We did exact same stuff against Nazis during WW2 for example Warsaw Uprising or even the brave jewish partisants from Warsaw getto when they arose agains germans.