Thomas Sowell explores for Human Events readers the political Left’s interest in something dubbed “micro-aggression.”

Professors at the University of California at Berkeley have been officially warned against saying such things as “America is the land of opportunity.” Why? Because this is considered to be an act of “micro-aggression” against minorities and women. Supposedly it shows that you don’t take their grievances seriously and are therefore guilty of being aggressive toward them, even if only on a micro scale.

You might think that this is just another crazy idea from Berkeley. But the same concept appears in a report from the flagship campus of the University of Illinois at Urbana. If you just sit in a room where all the people are white, you are considered to be guilty of “micro-aggression” against people who are not white, who will supposedly feel uncomfortable when they enter such a room. …

… “Micro-aggression” protests have spread to campuses from coast to coast — that is, from California’s Berkeley and UCLA to Harvard and Fordham on the east coast, and including Oberlin and Illinois in the midwest.

Academic administrators have all too often taken the well-worn path of least resistance, by regarding the most trivial, or even silly, claims of victimhood with great seriousness, even when that involved undermining faculty members held in high esteem by most of their students and by their professional colleagues on campus and beyond.

The concept of “micro-aggression” is just one of many tactics used to stifle differences of opinion by declaring some opinions to be “hate speech,” instead of debating those differences in a marketplace of ideas. To accuse people of aggression for not marching in lockstep with political correctness is to set the stage for justifying real aggression against them.

This tactic reaches far beyond academia and far beyond the United States. France’s Jean-Paul Sartre has been credited — if that is the word — with calling social conditions he didn’t like “violence,” as a prelude to justifying real violence as a response to those conditions. Sartre’s American imitators have used the same verbal tactic to justify ghetto riots.