For left-wingers on college campuses, spring cleaning involves more than dredging their dorms for pizza boxes from October. For at least the past two decades, students have also cleansed (if that’s the right word) their commencement ceremonies of speakers with whom they disagree on politics. They’ve tossed Condoleezza Rice, Alec Baldwin, Christine Lagarde and many others out of the proverbial window along with last semester’s late-night Dominoes order.