Pamela Newkirk is a professor of journalism at New York University and the author of “Spectacle: The Astonishing Life of Ota Benga.”

Derek Black was reared in the cradle of white supremacy.

His godfather and mentor was David Duke, and his father, Don, a former Ku Klux Klan grand wizard and founder of a popular hate website, plotted to overthrow the Caribbean island nation of Dominica to create a white utopia. As a child, Black’s bedroom was adorned with Confederate flags, and his head was filled with doubts advanced in online chat rooms about the Holocaust and about the intelligence of racial minorities. By age 10, Black had built a children’s website featuring racist and anti-Semitic songs and games that attracted more than 1 million visitors. Later he launched a 24-hour online radio network, and five days a week he hosted a show in which he peddled racial pseudoscience and advocated for a whites-only country. But just as the rise of the movement culminated in the election of Donald Trump, Black had a change of heart.

In “Rising Out of Hatred: The Awakening of a Former White Nationalist,” journalist Eli Saslow charts Black’s conversion from a right-wing extremist to a high-profile critic of the movement. Saslow, a Pulitzer Prize-winning reporter for The Washington Post, opens with a gathering of the nation’s “preeminent white nationalists” in Memphis in the fall of 2008. The meeting, organized by Duke and attended by 150 Klansmen and neo-Nazis, was animated by the election four days earlier of Barack Obama, the nation’s first African American president. “We can take the country back,” Black, then 19, declared. “The great intellectual move to save white people started today.”

Black, who once consoled fellow extremists by performing the 1972 song “The Monkey That Became President,” was considered a prodigy and the future of the movement. A few months earlier he ran for committeeman in Palm Beach County, Fla., on a platform of white victimhood, and he defeated a Cuban American incumbent. Beneath America’s credo of racial equality he found ample evidence of its white-nationalist heart. He was encouraged by Abraham Lincoln’s assertion, during his 1858 debate with Stephen Douglas, that “I as much as any other man am in favor of having the superior position assigned to the white race.” He felt his ideology was validated by James Monroe, Thomas Jefferson and other lions of American history, who held similar views. “It felt to Derek as if he were being let in on a secret,” Saslow writes. “White nationalism wasn’t just a fringe racist movement but something much more forceful and dangerous: a foundational concept embedded in the American DNA.”

But when he took up studies at New College, Florida’s four-year liberal arts honors college, his thinking slowly began to change. In speeches and on the radio he continued to preach white separatism and anti-Semitism, but at school he befriended classmates of Peruvian and Jewish backgrounds, and attended Shabbat dinners. His double life was exposed when a senior working on his thesis discovered him in a file of white extremists. The student posted links to Black’s articles and radio show on the school forum, sparking a campus-wide controversy that unfolded as Black was in the Alps meeting with Duke.

Although Black was widely ostracized on campus, he was befriended by Mike Long, a “popular student body president” who, Saslow says, “had never been afraid to talk to anybody, including a white supremacist.” Long invited Black on a boat outing, where Allison Gornick, a student who had previously shunned him, began to see him in a different light. “She thought he seemed quirky, gentle, and interesting — nothing like the extremist she had expected — and before long the sun had set and they were arriving at the marina,” Saslow writes.

Gornick figures prominently in the narrative as she repeatedly challenged Black’s bigoted views and nudged him to reconsider them. However, his evolution — characterized by evasion and contradiction — was halting and at times barely perceptible. “Derek didn’t use any slurs, and he told Allison that he respected all people,” Saslow writes. “He was simply a white nationalist, which meant he thought whites needed to be protected within their own border, like an endangered species.”

Later Black said he no longer supported the forced deportation of immigrants “but maybe gradual self-deportation . . . in which nonwhites would leave on their own.”

Throughout his metamorphosis Black struggled to cut the ties to his hateful past. “Derek told Allison that . . . he wasn’t a white supremacist,” Saslow writes. “He told her he had friends who were neo-Nazis, but he felt comfortable publicly rejecting Hitler-era Nazism.”

Eventually he supported affirmative action, Black Lives Matter and same-sex marriage, but Black’s constant dissembling and contradictions often render his thought processes opaque. For me, it was at times unclear what specific circumstances and conversations prompted his dramatic about-face. Saslow often turns to Gornick to decipher Black’s beliefs. “Only she knew how much [classmates’] exclusion had made him reconsider the ways his ideology oppressed others, and how their inclusion at Shabbat had helped him better empathize with minorities and Jews,” he writes.

But Saslow does recount one illuminating encounter — a turning point — when Black found himself revolted by his father’s views after the acquittal of George Zimmerman, the self-described neighborhood watchman who stalked and killed an unarmed Trayvon Martin. Black “thought again about everything his father had said publicly about Trayvon Martin. It was all typical stuff — the same ugly talking points [Black] had been hearing and often repeating for his entire life — so why did it make him so angry?” Saslow writes. “It wasn’t just his father’s views that suddenly horrified him. . . . It was the memory of his previous self. He had made versions of those same flawed arguments. He had expressed similar callousness, ignorance, and cruelty. It seemed obvious to him now that he needed to publicly condemn not only white nationalism but also his past life.”

Black then typed a letter and emailed it to the Southern Poverty Law Center, a civil rights group that has battled racism for decades. He admitted that his actions had been “harmful to people of color, people of Jewish descent” and others. “I will not contribute to any cause that perpetuates this harm in the future.” He then criticized the tenets of white nationalism. “It has become clear to me that white nationalism is not a movement of positive identity or of asserting cultural values, but of constant antagonism at the betterment of other groups. . . . I can’t support a movement that tells me I can’t be a friend to whomever I wish or that other people’s races require me to think about them in a certain way or be suspicious at their advancements. Minorities must have the ability to rise to positions of power, and many supposed ‘race’ issues are in fact issues of structural oppression, poor educational prospects, and limited opportunity.”

Black’s father, Don, at first thought the letter was fake, an attempt to disgrace the family. When he learned the truth he was shocked and sickened. But he and his son agreed on one key point: After they both spent years promoting its tenets, white nationalism had finally seeped into the American mainstream.

“Rising Out of Hatred” is a disturbing look at the spread of that extremism — and how it is planted and cultivated in the fertile soil of American bigotry. And yet, Saslow’s vivid storytelling also conveys that during this period of deepening racial division, there is the possibility of redemption.

Rising Out of Hatred

The Awakening of a Former White Nationalist

By Eli Saslow

Doubleday. 288 pp. $26.95