Open this photo in gallery: Nemat Shafik, the president of Columbia University, testifies during a House Committee on Education and the Workforce hearing on Capitol Hill in Washington, on April 17.AMANDA ANDRADE-RHOADES/The New York Times News Service Four months after a contentious congressional hearing led to the resignations of two Ivy League presidents, Columbia University’s president appeared before the same committee on Wednesday and unequivocally denounced antisemitism on her campus, rebutting claims that she has allowed Columbia to become a hotbed of hatred. “We condemn the antisemitism that is so pervasive today,” Columbia President Nemat Shafik said in an opening...