He did not have his identification with him. In a particularly humiliating ritual, the officers went to University Hall and asked two students to confirm that the professor had an office there. They did.  As these types of incidents accumulate, resentments build. Black students that I’ve spoken with at Harvard over the past week have not complained about overt racism or widespread police misconduct. Rather, they have expressed their sense of unease over encounters that others might dismiss as aberrations or think of as trivial but that collectively make the students feel as if they are being treated differently — unfairly — at their own school, and they don’t like it.  Nworah Ayogu, a senior who is studying neurobiology, told me about a well-known incident that occurred in 2007 when a number of black students were playing games like dodge ball and capture-the-flag on the Quad as part of an annual field-day-type celebration. White students called the Harvard police to investigate.  The police showed up on motorcycles and asked the black students for identification, even though the students were wearing all kinds of Harvard regalia — caps, crimson T-shirts with “Harvard” emblazoned in white, and so forth. Mr. Ayogu said the cops actually seemed to be embarrassed by the situation and were not confrontational.  “The whole thing made us feel like we didn’t belong,” he said. “What was most offensive was that our own classmates called the police on us.”  Harvard has made an aggressive effort to deal with these situations and create what the school describes as a more welcoming atmosphere for everyone. But it should be easy to understand that one distasteful encounter after another — not just at Harvard or in Cambridge, but nearly everywhere in this country — cannot help but lead to the expectation among blacks that cops will target people and treat them badly solely because of their race.  Too often that expectation is realized, sometimes tragically. Think Amadou Diallo, who died in a hail of police bullets (fired for no earthly reason) outside of his home in the Bronx.  No one is immune. Colin Powell told Larry King that he had been profiled many times. Attorney General Eric Holder spoke last week about how humiliated he felt as a college student when a cop made him stop his car and open the trunk so it could be searched for weapons.  No one is too young. I traveled to Avon Park, Fla., a couple of years ago to write about the arrest of a black 6-year-old named Desre’e Watson. She threw a tantrum in her kindergarten class. The police were called, and the terrified child was arrested, handcuffed (the handcuffs were too large to fit her wrists, so she was cuffed on her upper arms) and driven off to headquarters.  When I asked the police chief about the incident, he said: “Do you think this is the first 6-year-old we’ve arrested?”  Young, old, innocent as the day is long — it doesn’t matter. Your skin color can leave you perpetually vulnerable to a sudden and devastating criminal injustice.  David Brooks is off today.  A version of this op-ed appears in print on , on Page A23 of the New York edition with the headline: Innocence Is No Defense. Today's Paper|Subscribe
The arrest of Henry Louis Gates Jr. was the latest in a series of incidents that have left members of the Harvard community feeling unfairly targeted and humiliated because of their race.