Actually, if I recall from previously posted articles, Berthold is not a leftist. He's a member of the National Association of Scholars - a group opposed to things like campus "hate speech" codes, and academically questionable fields like "Womens studies."
That may explain why the university was happy to hang him out to dry over this.
You don't have to support speech codes to be a leftist. I think his little "joke" is a better indicator of his political orientation.