Ronald Crutcher, president of the University of Richmond (VA), writes:  The higher-education sector has witnessed significant angst and change during my lengthy career — from violent protests over what were believed to be unjust wars to increases in representational diversity to affirmative action challenges decided by the U.S. Supreme Court. Yet our recent propensity to disinvite speakers who are controversial, or with whom we don’t agree, is tearing our campuses apart.