It's possible to be pro-Jew and anti-Zionist, I hate the murderous Israeli Government for what they do to Palestinian children, and that's by no means anti-Semitic. Bravo, Labour leadership!
The Jewish lobby in the USA is strongly influenced by its many Christian fundamentalist members who refer to various crazy passages in the Book of Revelations to keep justifying the status quo
I suspect that the fundamentalists are primarily interested in delaying Armageddon, and that their agenda might not even be pro-Jewish! There are of course substantial differences between their warped religious agenda and the more reasonable aspects of Judaism.