In one of his most profound and stirring speeches, the Rev. Dr. Martin Luther King Jr. summed up the crucial divide between blacks and whites that continues today: “While the law cannot make a man love me, it can stop him from lynching me.”

The nation rejoiced last week that 50 years have passed since a historic Supreme Court decision, Brown v. Board of Education, supposedly cracked the back of Jim Crow. Yet suspicion and mistrust between the races bubble just beneath the surface of our profound sense of national achievement. Racism, segregation and discrimination continue throughout America; in some areas of the country, separation along racial lines is as implacable as ever. Blacks often segregate themselves from whites. Millions of minorities live out their lives with a separate consciousness.

“The differences that have always existed between blacks and whites did not disappear with the Brown v. Board ruling,” says Delores Driver, a longtime social worker in Baltimore. “You don’t erase long-standing barriers by fiat.”

Blacks have the strong sense that nearly every institution in America — the courts, housing, schools, churches, financial institutions, government, corporate boardrooms, the media, even beauty contests — has carved out separate places for minorities.

Sometimes black comedians like Dave Chappelle express such observations best. “When white people look in the mirror in the morning, they see a funny-looking, fuzzy-headed, sleepy individual getting ready for work. When blacks look in their mirrors, they see the same thing except the face is black and that is foremost.

“From the moment we awaken in the morning, we are conscious of color. As long as society sends signals that we are different and therefore inferior, America will never be a united nation.”

Funnyman Chris Rock speaks sarcastically about the “hypocrisy of our democracy.”

He insists he does not think that under the banner of affirmative action a black should be moved to the head of the line if he earns a lower score on a test than a white.

“But if our scores are equal,” Rock says with a shrug and a broad smile, “to hell with whites, because they had a 400-year head start on us.” His black audiences cheer.

Whites often insist the playing field was leveled by King and others during the turbulent 1960s. But walk into any cafeteria of most of America’s integrated schools, and you’ll find blacks lounging in one area of the lunchroom while whites gather in another. This underscores the schism in our society. Blacks often engage in self-segregation. Just as whites do, they feel greater comfort with their own group.

Many blacks believe whites offer only a grudging acceptance or tolerance, which is not voluntary but a response to the law. But that belief masks a much older resentment and distrust, with deep roots in history.

It should not be difficult for anyone to understand why those old televised images of blacks in the civil rights movement being battered by powerful water streams from fire hoses, bitten by attack dogs, and beaten to the ground with billy clubs, have not disappeared from the minds of minorities. It is a heart-wrenching history of abuse and power imposing its will on people denied the vote, service in restaurants or access to decent housing and schools.

Young blacks may not have known such discrimination firsthand, but they recall the all-white juries who sent their parents and grandparents off to jail, often on trumped-up charges. They’ve read about the lynching of their people, the laws that forced them to sit in the back of the bus, the indignity of “Whites Only” drinking fountains, even segregated graveyards.

Brown may have been historic, but what eats at minorities today are the indignities embedded in their past and those they continue to suffer. Resentment by blacks runs deep; it poisons the chances for trust in modern laws and the better impulses of more enlightened whites.

Claude Lewis is a retired columnist for the Philadelphia Inquirer.