The Tulsa minister calls a Holocaust-denial meeting in Iran 'appalling.'

A former Ku Klux Klan official criticized that group's former leader Thursday for attending a Holocaust-denial conference in Iran this week.

The Rev. Johnny Lee Clary of Tulsa said David Duke's appearance at the Tehran conference was appalling, and he called on more Americans to denounce Duke's trip.

He's also written a letter to the FBI to request an investigation into Duke's visit to meet with "known terrorists" such as Iranian President Mahmoud Ahmadinejad.

"If we allow Duke and all the Holocaust deniers to continue to teach people this nonsense, it's going to become a cancer that will destroy a society," Clary said from his civil rights ministry in Tulsa.

Ahmadinejad, who has called for Israel to be "wiped off the map," sponsored the world conference to question the Nazi Holocaust during World War II, in which 6 million Jews were murdered.

Clary, 47, who joined the Klan when he was 14 and at one point served as Duke's bodyguard, said he got angry when he saw recent news reports about the conference.

"For anybody to say the Holocaust never happened and try to convince the world that it's all a lie -- it's appalling," Clary said. "There's plenty of evidence; there's overwhelming evidence."

Duke called the Holocaust a "device used as the pillar of Zionist imperialism, Zionist aggression, Zionist terror and Zionist murder."

Clary spent 16 years in the KKK, rising to the post of Imperial Wizard, before he got out, realizing that the group was committed to hate and bigotry.

It was Duke, a white supremacist and former Louisiana state representative and candidate for president, who got him interested in joining the KKK, Clary said.

"One day, I turned on the TV and there's David Duke, speaking for the KKK," he said. "Keep in mind I idolized this guy. I thought he was some kind of hero."

Today as a civil rights motivational speaker, Clary runs Operation Colorblind Inc., aimed at ending racism around the world.

"Racism is a wall, and I feel like we need to keep chipping away at it, and it will come down," he said. "We've got to cut racism out of society like a cancer."