"Oh, he's brilliant, very brilliant," Nate Phelps says, a conflicted look of begrudging admiration and utter contempt on the round moon of his face.

He shakes his head. "He's got incredible capacity. And he's also an incredible speaker. He could sway juries…" He trails off, raising his eyebrows as he recalls a scene from his youth. "I watched him. He would take an issue and work it out and get down into the nuances of it. The minute details he would focus on." He pauses again, shaking his head. "That's a very good capacity when you're an attorney."

But Fred Phelps, the man he's talking about, is no longer an attorney. He's one of the most controversial pastors in the United States. Founder and leader of the virulently anti-gay Westboro Baptist Church in Topeka, Kan., and patriarch of the clan that was the subject of a BBC documentary called The Most Hated Family in America, he is Mr. Phelps's estranged father.

Story continues below advertisement

The irony is that the son is just as brilliant as his father, only his analytical mind is in search of a truth different from the religious one "hard-wired into my brain" as a boy, and the battle he has decided to wage is shaping up to be a made-for-TV faceoff.

For most of his life, Nate Phelps, now 51, has been silent. But last year, after a writer figured out who he was when riding in Mr. Phelps' taxi in Cranbrook, B.C., he went public. Mr. Phelps had moved to Canada to be with a woman he met online after a difficult divorce from his first wife, with whom he has three children and a stepchild.

At conventions in the United States and Canada - he was in Toronto earlier this month to speak at the Centre for Inquiry, a non-profit organization that promotes critical thinking - he has spoken out about his father's church, comprised mainly of Phelps family members. Many have called it a cult. His father physically abused all 16 of his children and his wife, Marge, who is now 85, he alleges. Two other children have left the family and changed their names.

A month ago, Mr. Phelps returned to Topeka to speak at a gay rally - a move that put him at the centre of his father's hate campaign.

Westboro Baptist Church members claim that God hates the United States because of its support for gay rights; they picket the funerals of soldiers killed in Iraq with signs saying the deaths are God's punishment.

"It was terrifying," Mr. Phelps says of his decision to speak at the rally.

"It was the first time I'd been there in any form to discuss it. [But]it was a very timid kind of pushing back against it," he avers. "It's not a real aggressive thing."

Story continues below advertisement

That comment strains credulity or perhaps speaks to Mr. Phelps' naiveté. A documentary film crew, associated with the Richard Dawkins Foundation for Reason and Science in California, a well-known atheist organization, was in tow, not just filming him but interviewing Phelps family members, including Shirley Phelps-Roper, his outspoken sister who is considered the de facto leader of the group now that Pastor Phelps is 80.

Asked about why he has chosen to go up against his father 30 years after leaving the church for the second (and final) time - the first was the day he turned 18 - Mr. Phelps reveals a complex set of reasons. Partly, there's a need for atonement, he acknowledges, but it's also an effort to gain momentum for a possible book deal.

The fact that Mr. Phelps, who now lives with his fiancée in Calgary, openly admits to the latter is a salient clue - this is a great towering man of wounds who is searching for a meaningful foothold in midlife. At least 6 foot 3 and well over 200 pounds, he is a jumble of emotions.

He talks of "tapes rolling in my head of my old man so critical of and hateful of any projection of positive feeling or emotion." He has spent many years worrying about his salvation, because his father had inculcated in him that God would punish anyone who didn't live according to his interpretation of the Bible.

Once Mr. Phelps had left his father's control, he would interpret every event as evidence of God's wrath - something as simple as a speeding ticket would be a sign of his impending damnation, he explains. Even though he understands that homosexuals don't choose their sexuality, doubt creeps into his mind when he defends them. "It isn't an intellectual thing. It's an emotional thing. It's what was hard-wired into my brain. And it whispers, 'What if I'm wrong?' "

Each day is still a struggle. "I'll go into depression, and I won't even know why," he confesses. He has tried therapy, but it hasn't helped very much.

Story continues below advertisement

The move to atheism was "a journey," he explains. In his 18-year marriage, he went to a garden-variety Christian church, but when his description of hell frightened his young son, he felt it wasn't right to control behaviour through fear. "That was a moment," he concedes gently.

"I don't accept the argument that growing up in a twisted environment is what led me to atheism," he says at one point.

"I accept the argument that growing up in a hyper-focus-on-God environment led me to search for answers. There's no doubt about that. And I do accept that there's damage there…I just don't see any evidence for a God. But I see plenty of evidence for good and evil in humans."

Does he feel love for his father? Can he forgive him? He visibly cringes at the questions. "I appear heartless and maybe I am," he begins. "But I just don't feel there's any love there." And his mother? (Ms. Phelps-Roper admits that they were all beaten as children as part of the Biblical edit, "Spare the rod, spoil the child" but she denies that their mother was physically abused.)

"I'm conflicted about my mother," Mr. Phelps says softly. "My overarching feeling about her is that she is a victim like everyone else."

He is evidence of good, I point out to him; that despite his background, he has emerged as a voice of reason and compassion. Isn't that worth something? "I have a hard time feeling that," he says.

Story continues below advertisement

Asked what keeps him going - he admits to having suicidal thoughts - he answers in a calm, resigned voice. "I think it's just constant hope that I'm going to find answers."