Henry Kissinger’s return to Harvard this week was a homecoming of sorts for a man who has conspicuously avoided his alma mater for at least three decades. Kissinger attended Harvard College, received his doctorate at Harvard, and became one of its most celebrated professors. But after he left in 1969 to become President Nixon’s national security advisor, Harvard faculty and students issued such scathing criticisms of his policies in Vietnam and Cambodia that he never came back.