When Thomas J. LeBlanc, president of George Washington University, was asked this month if he would have the institution divest from fossil-fuel companies if the proposal had student support, he reached for an analogy to argue that such pressure wouldn’t matter. “What if the majority of the students agreed to shoot all the black people here?” he said in an impromptu sidewalk meeting that was recorded on video. “Do I say, ‘Ah, well, the majority voted?’ No.”