If you want to understand the wrenching generational rift over Israel among many left-leaning American Jews, the documentary “Israelism,” which came out this year, is a good place to start. Much of it centers on the political evolution of Simone Zimmerman, who was raised to be a staunch Zionist, began questioning her beliefs even as she defended Israel at the UC Berkeley, and was transformed by her encounter with the harrowing reality of the Palestinian occupation. Zimmerman went on to co-found IfNotNow, an anti-occupation Jewish group that has been at the forefront of many protests against Israel’s war in the...