Singer Ian 'H' Watkins' has told of the "complete nightmare" of growing up gay in the south Wales valleys.
Ian 'H' Watkins said he was "flabbergasted" by the comments
The former Steps singer, who is from the Rhondda, filmed a personal account for BBC Wales' Week In Week Out.
In the programme, he also looked at schools' treatment of gay issues and admitted he was bullied "relentlessly".
Making the documentary, he said he was shocked to be told by one Christian campaigner that being gay made him no better than a serial killer.
Christian Voice director, Stephen Green, told Watkins his lifestyle was "sinful", and made him no better than US mass murderer Jeffrey Dahmer.
Mr Green also told the former Celebrity Big Brother contestant he could become straight if he wanted to.
The comparison to Dahmer who was jailed for life in 1992 after the Wisconsin trial heard evidence of his cannibalism after murdering his victims came when Watkins told Mr Green he was "completely happy" being gay and that he was in a loving relationship.
Mr Green added: "Jeremy (sic) Dahmer was happy murdering people, does that make it right?"
Jeffrey Dahmer murdered 15 young men and boys
The comment shocked Watkins and he responded: "So, being completely happy and at one with yourself, and being in a happy, loving relationship is the same as murdering somebody?"
But Mr Green stuck to his guns during the exchange: "Sin is sin...in the eyes of God, sin is sin..."
When Watkins referred to people being born gay, Mr Green told him: "I don't believe anybody is born homosexual. God wouldn't allow anybody to be born homosexual."
Watkins, who came out when he was in the Big Brother house alongside Shilpa Shetty and Jade Goody, says he was "absolutely flabbergasted" by the comments.
Watkins came out in the Big Brother house
Watkins, who is originally from Cwmparc, Rhondda, canvassed opinion on gay and lesbian people on the streets for the programme and talks about the prejudices he encountered growing up.
He said: "I'm gay, and today I'm completely open about it. But growing up here in the Rhondda, it was a complete nightmare."
He also talked about his time in the pop group Steps.
"Despite my success, I couldn't be myself. In a pop group like Steps, you need to be three things: single, sexy and straight.
"I had to lie about the last one."
Watkins also interviewed gay rugby referee Nigel Owens and said he was "amazed" there were no openly gay professional rugby players.
"Maybe the game's too tough. Or maybe they're just keeping quiet," Watkins added.
Week In Week Out is broadcast at 2235 GMT on Tuesday on BBC One Wales. Outside Wales, BBC One Wales is available on Sky channel 972.