On a warm November day, a group of Columbia University professors set up “listening tables” near the center of campus and hailed students rushing to class, inviting them to stop and talk. About a dozen students, alumni and faculty members sat down, grabbed some free pizza and chatted about how the protests over the Israel-Hamas war had alienated some of them and inspired others. Then, a woman in a kaffiyeh, the traditional Palestinian scarf, spoke up and the tension rose. Over the past...