This is an identity crisis that is most commonly seen among Jews, but far from alien to the rest of the West. Universalism has become the common form of moral rhetoric, the goal being to transcend parochial identities, to maximize diversity and teach the world to sing. "Don't the Pakistanis, Indonesians, Lebanese and Somalis have as much right to be in this country as we do," is the argument repeated from Sydney to London to Oslo. Substitute illegal aliens and you have the American version of it. The new 9/11 curriculum will ask students to decide whether America should defend itself, or embrace a "Global Buddy" system through soft power.
While the writer focuses on answering the question "Why are Jews liberal?", it's easy enough to generalize from his answer to answer the question "Why are there liberals?" I think the answer is the same.