Given the explosive excitement surrounding congresswoman Michele Bachmann's White House bid, it was perhaps no surprise that organisers of a Minneapolis conservative bloggers' conference, Right Online, over the weekend chose to introduce her with the infuriatingly catchy Katy Perry song "Firework".

Bachmann is now a real rock star of the hardcore Republican right and the Tea Party faithful. But the song choice showed a profound misunderstanding of popular culture. For Firework – whatever one thinks of its musical merits – is a gay anthem. The video Perry filmed to go with it preaches a message of universal tolerance and includes a young man coming to happy terms with his sexuality and kissing another man. Which, to put it mildly, is ironic for Bachmann and her legion of supporters.

For Bachmann is surely one of the most anti-gay mainstream candidates to run for the White House in recent years. A glance at Bachmann's record on gay issues shows a good part of her political philosophy and personal beliefs are based on preaching prejudice against a vulnerable minority of the American people. (One member of that community made her protest by "glitter-bombing" Bachmann as she left Right Online.) America has come a long way since segregationist George Wallace first ran for president in 1964. But swap blacks for gays in some Bachmann comments and it becomes clear that some politicians have come less far than others.

Bachmann has spearheaded fights to get a constitutional amendment banning gay marriage in Minnesota. That, in itself, is not too unusual. But what is unusual is the fervency of Bachmann's anti-gay agenda. Her stance does not seem cynical politicking to her base. It seems rooted in her core beliefs and evangelical religious outlook. Bachmann, after all, once hid behind some bushes to keep an eye on a gay rally in St Paul, Minnesota. In another notorious incident, when two lesbians once approached Bachmann in a bathroom to talk about her anti-gay opinions, the congresswoman claimed she was being kidnapped and fled to police to try and press charges (the authorities took a dim view of the complaint and declined to pursue the matter). In 2004, she called being gay "part of Satan". In the same year, she also compared it to slavery, saying:

"If you're involved in the gay and lesbian lifestyle, it's bondage. It is personal bondage, personal despair and personal enslavement."

She's said teaching young children about gay people is akin to child abuse and has claimed that gays have a "sexual dysfunction". She believes gays specifically target children and has said repeatedly that she believes America is on a path that will eventually see young people forced to "try" being gay.

Of course, for Bachmann, this is close to home. Her husband Marcus Bachmann – who is a major influence in his wife's political career and beliefs – runs a Christian counselling business in Minnesota. He has referred to gays as "barbarians":

"We have to understand that barbarians need to be educated, need to be disciplined. And just because someone thinks (they're gay) or feels it doesn't mean we need to go down that road. That's what is called the sinful nature."

Marcus Bachmann has denied that he runs courses seeking to "cure" people of their homosexuality. But in 2005, he spoke at a conference and, according to a gay activist present, ended his presentation with testimony from three people who claimed to have been "cured" of their gayness and were now straight. His speech was called "The Truth About the Homosexual Agenda".

But what is really scary about Bachmann's anti-gay beliefs are how they have run roughshod over her own family life. Some high-profile conservatives, such as former Vice President Dick Cheney, have softened their stances or embraced gay rights because they have out and proud members of their own family. Just this week, New York Post columnist Andrea Peyser shed her normally strident conservatism to write a moving tribute to the lesbian marriage of a favourite niece. But Bachmann stays rigid even when her own family members are gay.

Bachmann's step-sister, Helen LeFave, is a lesbian. The two were close as they grew up together in their teens. Not surprisingly Bachmann's anti-gay comments have not gone down well with her, or several other relatives. They have written letters to newspapers opposing Bachmann's stance or appeared at political hearings on attempts to ban gay marriage. Yet, even in the face of having gay relatives in her own family, Bachmann is unwavering. No doubt, that is what many of her fans love about her.

She is a real conviction politician in an era where most presidential aspirants love their focus groups first and foremost. But what a shame one of Bachmann's core convictions is naked prejudice against some of her fellow citizens and a wish to deny them the basic rights afforded to everyone else.

• Editor's note: this article originally gave the location of the gay rally on which Bachmann spied as Washington, DC; the incident took place in St Paul, Minnesota. The article was amended at 4.45pm (BST) on 22 June 2011