When I was growing up, national black leaders were also educators for us all: Roy Wilkins (NAACP), Whitney Young (National Urban League) and A. Philip Randolph (labor organizer and compelling integrationist). Today, however, Jesse Jackson and Al Sharpton are not of that leadership quality — functioning more and more as self-promoters than educators.

But Dr. Bill Cosby (Ph.D. in education, University of Massachusetts) has become a major, forthright spokesman for what can and must be done to carry forward the work of earlier generations of black leaders in what A. Philip Randolph called “America’s unfinished (civil rights) revolution.”

Cosby’s spirit and energizing candor courses through an important new book — Juan Williams’s “Enough: The Phony Leaders, Dead-End Movements and Culture of Failure That Are Undermining Black America — and What We Can Do About It” (Crown Publishers).

Williams of National Public Radio is also an independent political analyst for the Fox News Channel, and wrote “Thurgood Marshall: American Revolutionary” and “Eyes on the Prize: America’s Civil Rights Years, 1954-1965.”

Williams’s rallying cry, “Enough,” would have gladdened the heart of my friend, the late Bayard Rustin, a key strategist for Dr. Martin Luther King Jr. Like Cosby, the prizes for Bayard were education that works, upwardly mobile jobs and a culture of self-respect based on achievement.

“Black politics (now),” writes Williams, “is still defined by events that took place 40 years ago … As a result, black politics is paralyzed. Late 20th-century black politics grew out of a youthful, vibrant civil rights movement … (while) today national black politics is dry and dusty with age.”

What has stirred up a lot of that dust, and continues to, was Cosby’s speech on the 50th anniversary of the 1954 Supreme Court’s Brown v. Board of Education ruling that segregated public schools are unconstitutional. (In 2006, there are more largely segregated public-school systems than there were in 1954.)

Cosby has since refused to stop focusing on — as Clarence Page noted in the Aug. 12 Washington Times — “the crime, violence, school dropouts, out-of-wedlock births … among black youths left behind by civil rights reforms.”

A corollary blight, Williams emphasizes in speaking about his book, is the popular culture of “too many of our young black people. It tells our young minds, searching for a strong and proud racial identity, that real blackness comes with hard, cynical ‘gangsta’ attitudes and dressing like a convict with your pants hanging down. It offers images of women … getting their sense of self-worth from dressing like oversexed toys for boys.”

But Cosby, as Williams points out in “Enough,” is urging “people to invest in their neighborhoods by not putting up with crime, even if it is committed by their own children or the boy next door, (and) he called for poor people to get guns out of their community …

“He told neighbors to watch out for all the children in the community and not to be ‘scared’ to tell the parents and the police when children are running wild.” This amounts, Williams emphasizes, to picking up “on the black American tradition of self-determination and self-empowerment.”

Those were the roots of the civil-rights movement — the courageous sit-ins at southern lunch counters; Marshall’s drive toward Brown v. Board of Education; the marches on Washington by A. Philip Randolph that inspired King and Rustin. But this reinvigoration of self-determination has led to the reviling of Cosby by such black critics as University of Pennsylvania humanities professor Michael Eric Dyson, who accuses Cosby of “blaming the poor” for the current political and economic forces that are widening the gulf between the poor and the rest of this country.

Dyson chooses to ignore that Cosby is trying to move black people to restore the energy, the momentum of the civil-rights movement to deal with those institutional and political breeders of inequality.

What is missing, however, from “Enough” is another book — or a documentary series on National Public Radio written and hosted by Williams — to show what is actually happening now, across the country, by black community leaders, teachers, young organizers, parents, preachers, politicians not beholden to party lines, who go beyond slogans and memories to bring back alive not just the words and the tune of “We Shall Overcome,” but the true grit of those who made a difference then — but knew there was so much more to do.

In 1937, a former slave told what it was like in 1865 (during the Emancipation): “Hallelujah broke out … Everybody went wild. We all felt like heroes, and nobody had made us that way but ourselves.”

(Nat Hentoff is a nationally renowned authority on the First Amendment and the Bill of Rights and author of many books, including “The War on the Bill of Rights and the Gathering Resistance” (Seven Stories Press, 2004).)