Story highlights People who perform same-sex marriages could face up to seven years in prison

Ugandan President Yoweri Museveni signed an anti-homosexuality bill Monday

The White House says Museveni took his country a "step backward"

Museveni changed positions on the bill several times before signing it

President Yoweri Museveni, who made anti-homosexuality laws in Uganda much tougher Monday, told CNN in an exclusive interview that sexual behavior is a matter of choice and gay people are "disgusting."

After signing the bill that made some homosexual acts punishable by life in prison, Museveni told CNN's Zain Verjee that, in his view, being homosexual is "unnatural" and not a human right.

"They're disgusting. What sort of people are they?" he said. "I never knew what they were doing. I've been told recently that what they do is terrible. Disgusting. But I was ready to ignore that if there was proof that that's how he is born, abnormal. But now the proof is not there."

Museveni had commissioned a group of Ugandan government scientists to study whether homosexuality is "learned," concluding that it is a matter of choice.

"I was regarding it as an inborn problem," he said. "Genetic distortion -- that was my argument. But now our scientists have knocked this one out."

Dean Hamer, scientist emeritus at the National Institutes of Health, wrote an open letter to the Ugandan scientists in the New York Times last week urging them to reconsider and revise their report. Among his responses to their conclusions: "There is no scientific evidence that homosexual orientation is a learned behavior any more than is heterosexual orientation."

Museveni, whose public position on the measure changed several times, signed the bill into law at a public event Monday. The bill was introduced in 2009 and originally included a death penalty clause for some homosexual acts.

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The nation's Parliament passed the bill in December, replacing the death penalty provision with a proposal of life in prison for "aggravated homosexuality." This includes acts in which one person is infected with HIV, "serial offenders" and sex with minors, according to Amnesty International.

The new law also includes punishment -- up to seven years in prison -- for people and institutions who perform same-sex marriage ceremonies, language that was not in the 2009 version of the bill.

Lawmakers in the conservative nation said the influence of Western lifestyles risked destroying family units.

The bill also proposed prison terms for anyone who counsels or reaches out to gays and lesbians, a provision that could ensnare rights groups and others providing services to lesbian, gay, bisexual and transgender people.

The White House issued a statement Monday: "Instead of standing on the side of freedom, justice, and equal rights for its people, today, regrettably, Ugandan President Museveni took Uganda a step backward by signing into law legislation criminalizing homosexuality."

The statement continued: "As President Obama has said, this law is more than an affront and a danger to the gay community in Uganda, it reflects poorly on the country's commitment to protecting the human rights of its people and will undermine public health, including efforts to fight HIV/AIDS. We will continue to urge the Ugandan government to repeal this abhorrent law and to advocate for the protection of the universal human rights of LGBT persons in Uganda and around the world."

United Nations High Commissioner for Human Rights Navi Pillay also denounced the law, saying it institutionalizes discrimination and could promote harassment and violence against lesbian, gay, bisexual and transgender people.

"This law violates a host of fundamental human rights, including the right to freedom from discrimination, to privacy, freedom of association, peaceful assembly, opinion and expression and equality before the law -- all of which are enshrined in Uganda's own constitution and in the international treaties it has ratified," Pillay said in a statement.

Museveni also told CNN that the West should not force its beliefs onto Ugandans.

"Respect African societies and their values," he said. "If you don't agree, just keep quiet. Let us manage our society, then we will see. If we are wrong, we shall find out by ourselves, just the way we don't interfere with yours."

He also said Westerners brought homosexuality to his country, corrupting society by teaching Ugandans about homosexuality. The West has also helped make children at schools homosexual by funding groups that spread homosexuality, he said.

Attitudes against homosexuality are prevalent in Uganda. A 2013 report from Pew Research found that 96% of Ugandans believe society should not accept homosexuality.

Thirty-eight African countries have made homosexuality illegal. Most sodomy laws there were introduced during colonialism.

Even before Museveni signed the bill into law, homosexual acts were punishable by 14 years to life in prison.

Ugandan gay rights activist Pepe Julian Onziema told CNN's Christiane Amanpour that some gay people in Uganda would rather kill themselves than live under the new law.

"Prior to the bill becoming law today, people attempted suicide because they are like, 'I'm not going to live to see this country kill me -- so I would rather take my life.' "

Many have already left the country in fear of violence, Onziema said, and among those who stay, many are stopping their activism.

Onziema, however, says he is not afraid. He says he won't let the law take away his voice.