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"Rabbi... Eckstein...predicts that Foxman's call for a united Jewish front is doomed to fail, since other Jewish leaders won't want to take on the religious right."
The other Salon article you reference, about Sharon and the end times eschatology(or looniness, if you prefer), points to the underlying reason that Eckstein is correct: American Jewry recognize the rabid anti-semitism just underneath the surface of certain Christian right-wingers who say they support Israel, even if that recognition is somewhat inchoate. The loony Christian right have to hate somebody, and as soon as they get bored hating Arabs they'll turn back to the Jews.
Jews allied with the nutso neocons are a little like battered wives sticking up for their husbands. They ask themselves, "what else are we going to do?"