In the past week, Knox College, a small private college in rural Illinois, has been dealing with the anti-Semitic screeds of a visiting assistant professor, Kwame Zulu Shabazz, whose credentials are conspicuously absent a doctorate, typically required for a school that presents itself as a distinguished liberal-arts college.

The “Old Main” building at Knox College. Credit: Knox College.

Mr. Shabazz traffics in hackneyed anti-Semitic tropes worthy of the Nazi rag Der Stürmer. They also have the all-too-familiar refrain of themes espoused by the Nation of Islam, exhortations that the Rev. Louis Farrakhan has publicly articulated for decades.

This is underscored by Mr. Shabazz’s showing of an interview with the Farrakhan in most of his courses. Farrakhan has blamed Jews for the 9/11 attacks, as well as the trans-Atlantic slave trade. The Nation of Islam’s printed works about the Jews and the trans-Atlantic slave trade are so filled with deception that in 1995 the American Historical Association issued a statement condemning “any statement alleging that Jews played a disproportionate role in the Atlantic slave trade.” Henry Louis Gates, Jr., then chair of the Department of African American Studies at Harvard University, also denounced the work, calling it demagoguery by pseudo-intellectuals.

If these are the ideas being disseminated at Knox College for the annual tuition of $44,000 a year, then I would suggest that students immediately go to the bursar’s office and seek a refund for being exposed to concepts that are merely anti-Semitic propaganda masquerading as scholarship.

As a citizen, Mr. Shabazz has the right to say what he wants. The First Amendment was not designed to protect popular speech; it was designed to protect unpopular speech. It was not designed merely to protect affirming speech but also hate speech. Yes, hate speech is constitutionally protected.

Indeed, Mr. Shabazz is somewhat more respectable when he is at least honest about his anti-Semitism. Claiming that he uses the word “Jews” when he really means “Zionists” or “Israelis” is laughable coming from a person who teaches an ethnic-studies course.

Does Mr. Shabazz have the right to introduce hatred into the classroom before a captive audience of impressionable students who are in a disadvantaged hierarchical relationship with the good professor? Equally important is whether he does that.

Where the rubber meets the road in these situations is over the question of what he does in his classroom. Mr. Shabazz has the right to be a crackpot on his Facebook and Twitter pages. If, however, Knox College is concerned about the intellectual integrity of his courses and scholarship, that is a far and away different matter.

If you want to teach that the Earth is flat, you are free to do so, but no college need accommodate you. If you want to teach that Zionism is genocide, you might want to explain this slogan in the context that the Palestinian population is one of the fastest-growing populations and according to U.N. projections will outstrip the Jewish population by 2035. If Zionism is genocide—as Mr. Shabazz has asserted—then the Jews seem terribly inept at it.

If you teach that Israeli Jews are European while ignoring that roughly half of all Israelis are descendants of Middle Eastern Jews expelled from Muslim lands between 1948 and 1967, you would be distorting history to disseminate propaganda. You would be abusing the very privilege of being a professor.

Colleges, like all communities, are made up of people with diverse intellectual talents, commitments and moral standards. During my years in academia, I have known some real eccentrics and people who were zealous bigots in their private life. I had a colleague who thought colonialism was a wonderful system because inferior people needed the guidance of their racial superiors. I had a famous colleague who was a well-mannered and cultured gentleman and a public anti-Semite. Neither of these men—much to their credit—brought their politics into the classroom or to faculty social occasions.

So, the real question for the Knox College community is not what Mr. Shabazz is putting on his Facebook page and tweeting, but rather what is he doing in the classroom? You are free to be a bigot in your private life, but you cannot substitute your bigotry for scholarship simply because you have an academic title. And no school, prestigious or otherwise, should let you do that.

Abraham H. Miller is an emeritus professor of political science, University of Cincinnati, and a distinguished fellow with the Haym Salomon Center. Follow him @salomoncenter.