On the surface, recent protests that shut down lectures on college campuses by provocative conservatives Milo Yiannopoulos and Charles Murray look pretty much the same — right down to the self-flagellating responses of the host institutions.

Leaders of the University of California at Berkeley, where demonstrators damaged property before a scheduled appearance by Yiannopoulos last month, and Middlebury College, where Murray was swarmed by a mob last week, lamented their schools' failures to live up to free-speech ideals.

Of the two episodes, however, the one involving Murray is a far better example of threats to free speech — specifically speech that comes from the far-right end of the political spectrum.

In the simplest terms: Murray, a scholar at the American Enterprise Institute, has ideas to debate; Yiannopoulos, who resigned from Breitbart News two weeks ago, does not.

Murray is best known for co-authoring “The Bell Curve,” a 1994 book that promoted the notion that the historical disparity in IQ test scores between black people and white people could indicate the genetic, intellectual superiority of one race over another. The New York Review of Books wrote the following about “The Bell Curve” at the time:

Certain of the book’s major factual contentions are not in dispute — such as the claim that blacks consistently have scored lower than whites on IQ tests, or that affirmative action generally promotes minorities who scored lower on aptitude tests than whites. And obviously intelligence is both to some degree definable and to some degree heritable.

The interpretation of those data, however, is very much in dispute.

That's a spot-on summary. Alternative explanations for the score gap cited by Murray include the many educational and socioeconomic advantages historically enjoyed by whites. Plus, there is a legitimate debate about whether IQ tests even do what they purport to do (measure intelligence).

It is certainly fair to argue that Murray's interpretation of data — white people might be inherently smarter than black people — is flat-out wrong, not to mention wildly offensive. It is fair to argue that his writing is motivated by racism. But at least there is something to argue about.

Yiannopoulos does not offer even that much. A professional contrarian, his whole shtick is saying things he considers politically incorrect — things like this, which are unprintable in this space. He finally went too far, even for some colleagues at Breitbart, when he said that “pedophilia is not a sexual attraction to somebody 13 years old, who is sexually mature.”

Yiannopoulos follows an attention-getting formula: He provokes outrage, then complains that his right to free speech is being trampled by everyone who says he can't say whatever he just said. Interpreting data? Not really his thing. A theory of, well, anything? Nope.

That's not to say that the people who smashed windows at Berkeley were justified. But Yiannopoulos does not represent an opportunity to engage in a meaningful discussion. Murray does. And the Middlebury students who disrupted his talk cost others — and themselves — that opportunity.