There is this essay by Nissan Ratzlav-Katz in The National Review Online, which explains why the "progressive" left abandoned its support for Israel after the Six Day War and to this day favors the Palestinians.
...the liberals in the United States preferred an Israel that was weak and needy — a perpetual, objectified victim...Liberals like victims. They need them....Without victims, liberals lose their raison d'etreThat may explain why liberals are so anxious to see Israel returned to what the former Israeli ambassador to the United Nations, Abba Eban, called the "Auschwitz borders" of pre-1967. That may also explain knee-jerk liberal support for the Arabs in Judea, Samaria, and Gaza, who appear by all standards to be victims — even if it is mostly due to their own leadership, their own hatred and their fellow Arabs