Many support diversity of opinion on the grounds that it is educational. That means, though, that we want diversity of opinion where that is educational. It doesn’t follow from this that any and all opinions are worth hearing. The point of diversity of opinion is not just so we can have false opinions leavening our diet of dull facts and reasonable points of view. The point of diversity is to help us learn what is right. Some opinions don’t deserve a hearing in an educational institution. It is thus not only permissible but morally obligatory to bar some speakers from campus—otherwise we fail in our responsibility as educators.
One obvious fact about education is that it is always selective. What we teach in the classroom is a function of choice, choice as to what will work best for our educational goals. The semester is finite; even four years is not enough time to teach all that we would like to. Thus, we naturally reflect on what courses to offer, and within those courses, which readings to assign and what ideas to present. Is our goal to present the widest possible diversity of ideas? Of course not. Our goal is to present the ideas, factual claims, interpretations, theories, and methodologies that we think are most plausible. Who wants a physics professor who presents outmoded theories of cosmology as if they were accepted fact? No one. While a given physics theory may turn out to be false, at the time the professor teaches it she believes it to be correct. In a case where there is no consensus among the informed on what is correct, a professor presents the major contending theories. Anything else is a waste of the students’ time, and not what justifies the costs of tuition. What if the professor teaches both the true theory and the false theory, just to represent diversity of opinion? Most teachers will say that they barely have time to teach all the correct stuff they need to in the course of a semester, and to spend any considerable time on rejected theories would be a waste. One could, of course, where it is a useful exercise, look at a rejected theory and explain why it was once believed and why it is now seen to be false. Simply teaching both true and false theories and leaving it up the student to choose for herself is not, even when she is encouraged to use her critical faculties, the best way to learn. For one thing, as said, it limits the time available to teach correct theories. For another, an undergraduate, even a talented one, may well not yet have the intellectual tools required for assessing theories and determining which is well-founded.
True, there are sometimes questions as to which of several relatively plausible theories is correct in a given case. While some theories have been definitively rejected, others vie for acceptance even among the experts who are well able to evaluate them. These theories address complex issues, and often it takes time and research to see which makes the best sense. Indeed, time may not be enough in some cases where the decision must be made by reasoning alone, in the absence of corroborative evidence. This may be more of an issue in fields that don’t lend themselves to empirical evidence, such as philosophy. In these cases it is perfectly reasonable to present different views, be it differing theories about the origins of romanticism, the nature of knowledge, or the true causes of the Reformation. We do this with the understanding not simply that either of two conflicting theories might possibly be right, but with the belief that both are views supported by good arguments. There are some good reasons to believe either one, and neither is definitively ruled out. Thus, since both are contenders, it is a good idea to expose students to both. They may then use their critical skills to choose between them, given the understanding that the truth is so far unknown.
So, in the classroom we don’t teach things we are certain are false, while we do allow assessment of competing theories when any one of the theories concerned is plausible. Why should talks that occur outside the classroom be different? Why would an academic institution whose goal is education invite speakers whose opinions are clearly wrong? Richard Spencer, for example, is a racist: his views are clearly wrong. What would be the point of allowing him on a campus whose goal is education? If anyone argues that we can never know if a view is clearly wrong, they should review the criteria for in-class teaching—that views must be at least plausible to be worth discussing, and that we do feel confident in declaring that some are not worth our time. It is probably true that for any clearly wrong view there is presumably some very remote possibility of its actually being true, if it is at least internally consistent, but such remote possibilities don’t justify inclusion in a classroom curriculum intended to educate. Why should campus venues outside the classroom open to the propagation of falsehood?
We face many complex, difficult issues and in some cases different approaches to these may in fact be just what we need. Contrasting reasonable opinions provoke thought, and even views that ultimately turn out to be false can give rise to insights as we consider them. This isn’t true of any and every false view, though. We don’t expect scientists to include the views of Flat-Earthers in their curriculum, or Creationism, or astrology. Even though some people believe these, they are false, and while sociologists may be interested those support such theories, considering the views on their merits is not fruitful because they have no merits—no rational basis. We don’t want to take the fact that many of us are eager to accept racism as evidence that the equality of the races is a complex, difficult question. We can be eager to accept beliefs that are both simplistic and false. Educational institutions exist to aid in enlightenment. Where there is ambiguity, this involves the use of critical evaluation of arguments on all sides. Where there is no ambiguity, it does not. Campuses are different from the public street precisely because they have this mission. Colleges and universities should, then, be a haven from nonsense.