White supremacist Richard Spencer’s appearance at the University of Florida last week was the latest flare-up in the debate over free speech that has roiled university campuses nationwide. First Amendment advocates have condemned Mr. Spencer’s views but insisted on his right to speak. Others believe that his hate speech should be suppressed because it is cruel, dangerous and antithetical to the values of diversity, inclusion and reasoned, respectful discussion.

Thankfully, Mr. Spencer came and went with little incident. But...