Now comes David Horowitz, a self-described former leftist radical who, since middle age, developed into a one-man cottage industry who plies controversial conservative schlock as his stock in trade.

His pet causes include the fight against “political correctness” on college campuses. He has written a book devoted to identifying the “101 most dangerous academics in America.”  He has crusaded against payment of “reparations” to the descendants of African-American slaves, as though that actually might happen sometime. He’s shown a deep capacity to conjure up conspiracies in which civil libertarians may be cast in league with terrorists and other evil doers.

Mr. Horowitz’s prowess at self-promotion has been in full display on college campuses in recent years through a program called “Islamo-Fascism Awareness.” It purports to bring to light how universities are “allowing an unholy alliance to form between the forces of terror and the forces of anti-Americanism.”

College Republicans at St. Louis University recently took the bait and organized “An Evening with David Horowitz: Islamo-Fascism Awareness and Civil Rights” on campus.

Not so fast, said SLU administrators (understandably) concerned that Mr. Horowitz’s talk could be seen as “attacking another faith and seeking to cause derision on campus.” They “offered the students several suggestions to modify their program in a way that could achieve their aims while remaining true to the University’s Catholic, Jesuit mission and values,” such as engaging “scholars with expertise on historical and theological aspects of Islam to help prepare their program.”

The College Republicans declined, deciding instead to pursue “other options,” according to SLU’s press office.

Noble intentions notwithstanding, the SLU administrators would have done better not to interfere. Mr. Horowitz’s unfiltered presentation itself probably would represent a compelling lesson in intolerance, sharpening students’ skills in debunking nonsense.

A recent controversy over a letter to the editor published this summer in The Arkansas Democrat-Gazette illustrates the point. The letter writer wrote:

“Wake up, white, Anglo-Saxon America. These white liberals like Billy Boy Clinton and his wife and Teddy Boy Kennedy have handed this whole country on a platter to these Africans. It’s probably too late, but the white and other races should be screaming loud and clear that enough is enough. These miserable liberals have been aided and abetted by the Jewish network.”

The letter upset some readers. They wished it never had been printed. The newspaper’s editors explained their decision:

“Misery is a hard dog to keep under the porch. It ranges far and wide, and it doesn’t have a political party, ideology or skin color. It’s an equal-opportunity predator… Would you rather that such thoughts just be allowed to fester in the dark? Let’s turn over this rock and see what’s underneath — and let a little sunshine in.”

David Horowitz is not as blunt or crude as the Arkansas letter-writer. But he, too, peddles anger and misery. To inject rigor and scholarship around his presentation, as SLU administrators suggested, would elevate him to a position he does not deserve.

SLU students could have learned much more by seeing the overturned rock laid bare under a bright light. They totally would have gotten it.