Do you believe this is the reason why Judaism has manged to exist for so long? I mean, nothing unifies people more than a simpleminded perception of the "us and them," especially when its rooted in hatred and a history of oppression.

It probably has something to do with it. I don't know what it is about humans, but when they cluster into groups which think they're special from all other groups, external hatred tends to make them even more cohesive and determined.

Another reason is probably due to the fact that Christianity and Islam have spread to very large chunks of the world, and yet neither make any sense without an a-priori acceptance of the Judaic idea of monotheism, and that this God has a "chosen" people who he established a relationship with through Abraham. The bad news for the Jews was that both Christians and Muslims claim that their respective religions superseded Judaism, and thus Jews were no longer God's chosen people. This issue is called supersessionism. (The term applies specifically to Jewish-Christian relations but the concept applies to Jewish-Muslim relations too.)

The Jews claim to be "chosen" by God. So do Christians and Muslims -but the Jews existed first… and thus the clash. Any successor will have issues establishing his legitimacy if the person/group he claims to have succeed actually still exists and rejects him.

The only other "chosen" people who can, by the logic of their own religions, get along with the Jews, are the religious groups whose "chosenness" developed entirely independently from the Judaic one and thus isn't threatened by the original Judaic claim of chosenness.

The idea that Jews (or any other group) are hated simply because they are "different"… I believe is false. You don't hate someone… just because they're different. If they're that different you probably don't even understand them in which case you would either pay no attention to them at all or you wouldn't care about them. A hatred depends on a certain level of understanding and comprehension. There must be something there to actually hate, and you'd have to comprehend it. You might watch a modern hollywood film in the English language and hate it. It strikes a cord and you have issues with it. But a film in a foreign language you don't understand, full of cultural references/images/music/scenes etc which mean nothing to you… how on earth would it be possible to hate it?

I think it is also worth mentioning that "Judaism" has undergone many, many changes since it first appeared. Judaism today (Rabbinic/Talmudic Judaism*), is actually younger than the oldest Christian churches. You can label it the same religion, sure, but I would claim that what goes by the name "Judaism" today is a separate religion from the Judaism which existed prior to the whole Jesus story/Roman expulsion from the land etc.

I know that Judaism claims that the Talmud (etc) are the oral commandments given to Moses *along with the written ones… but I really doubt that. I could actually be wrong, I admit, I don't know that much about it, but I find it extremely convenient that supposedly long existing oral commandments came to save the today when scripture wasn't enough. It would be like the Catholic church claiming to have kept hidden for thousands of years a "non-written bible", and finally today it's time to reveal it… and suddenly the whole religion changes. I find it hard to swallow.

My two cents.