In her new best-seller Ann Coulter breaks with the politically correct history of the civil rights movement by openly criticizing Rev. Martin Luther King Jr.

The always provocative Coulter makes the case that King’s embrace of mass street protests, specifically breaking the law by staging marches without permits and gaining public sympathy by purposely putting children in the way of vicious dogs and blasts from power water hoses used by rabid segregationists, is a prime example of how liberals throughout history get their way by using angry, inflammatory mob behavior.

Coulter writes in her book “Demonic: How the Liberal Mob is Endangering America,” that “Martin Luther King Jr. ...used images in order to win publicity and goodwill for his cause, deploying children in the streets for a pointless, violent confrontation with a lame-duck lunatic: Theophilus Eugene ‘Bull’ Connor,” the Birmingham sheriff who was known to be easily provoked to brutality and violence to enforce racial segregation.

She spoke with me as she was writing because I am the author of several books on the civil rights movement, including “Eyes on the Prize – America’s Civil Rights Years.” And she uses quotations from my best-selling biography of Thurgood Marshall, the liberal legal giant who became first black justice of the U.S. Supreme Court. Marshall, like Coulter, was a critic of King’s tactics.

“Thurgood Marshall had always disdained King’s methods, calling him an ‘opportunist’ and ‘first rate rabble-rouser,’” Coulter argues in her book. “Indeed, when asked about King’s suggestion that street protests could help advance desegregation, Marshall replied that school desegregation was men’s work and should not be entrusted to children. King, he said, was ‘a boy on a man’s errand.’”

You have to give Coulter points for shrewdly using the words of one black liberal civil rights icon to indict another liberal black liberal civil rights icon. She has a conservative agenda and she is a world-class provocateur who knows how to inflame her liberal critics.

Coulter and I disagree most of the time, especially on her regular use of harsh, partisan hyperbolic language to caricature people. Her tirades against liberals get lots of media attention and sell books but they overshadow the serious insights she has into American history. And when Ann is right, Ann can be devastatingly right.

In any case, Marshall worked to achieve racial equality by ending laws that discriminated against Americans in schools, in playgrounds, housing, on juries and at work. And he told me over the course of months of interviews of his differences with King. “I used to have a lot of fights with Martin about his the theory.”

Marshall said in one interview as we discussed King’s street protest tactics. “I didn’t believe in that. I thought you had the right to disobey the law and you have the right to go to jail for it.” In the same interview, Marshall conceded that King had tremendous influence. “He came up at the right time,” he said. “I think he was great – as a leader. As an organizer, he wasn’t worth s—t..He was a great speaker...but as for getting the work done, he was not too good at that…All he did was dump all his legal work on us (the NAACP) including the bills. And that was all right with him so long as he didn’t have to pay the bills.”

In those interviews I learned that there were times when Marshall deeply resented King’s fame – particularly when Martin Luther King Jr. Day was made a federal holiday.

The left often has a simplistic view of the civil rights movement as monolithic. The truth is that Marshall and King represented very different approaches to ending the bitter history of segregation. Marshall favored using the law while King favored bold demonstrations to gain media attention.

History tells us that both the demonstrators and the lawyers played vital roles in bringing about the end of segregation in America. But Marshall’s more conservative view of how to create lasting social change is often forgotten because he never wore a dashiki or patronized the idea of race riots as helpful to achieving racial equality. He was seen by many of the 60’s activists as a boring, law and order, establishment judge who deeply believed in the Constitution, loved America and was a social conservative.

How is it boring to win the landmark Supreme Court decision to end school segregation – the Brown decision – and break barriers as the first black Solicitor General and Supreme Court Justice?

Coulter’s brand of vituperative political commentary has sometimes poisoned our political discourse over years. She and her fellow provocateurs on the far right are featured prominently in my upcoming book “Muzzled: the Assault on Honest Debate.” But even a stopped clock is right twice a day. On this one, Coulter has her history exactly right and that is why the left is screaming.

Juan Williams is a writer, author and Fox News political analyst. His next book is "Muzzled: The Assault On Honest Debate" (Crown/Random House) which will be released in July.