WATCH: Prisons Show Being Gay's a Choice, Says Ben Carson

Ben Carson, the conservative Maryland doctor who is considering a run for the White House, has declared that being gay is "absolutely" a choice, in an interview that aired today on CNN.

The retired neurosurgeon, who just announced the formation of a presidential exploratory committee, told CNN's Chris Cuomo that ex-cons prove his point. "A lot of people who go into prison go into prison straight -- and when they come out, they're gay," Carson said. "So did something happen while they were in there? Ask yourself that question."

"The only thing that's really been proven here is that when Ben Carson says what he really thinks, he reveals himself as utterly unfit for office," said Fred Sainz, the Human Rights Campaign's vice president of communications, in denouncing what the organization called Carson's latest anti-LGBT rhetoric. "Ben Carson is putting his own personal ambition ahead of medical science by suggesting that a person can change their sexual orientation. As a doctor, Carson surely knows that countless mental health and medical organizations have condemned the idea that you can change a person's sexual orientation."

Before this, Carson has compared homosexuality and same-sex marriage to pedophilia, bestiality, and murder. He has also called for Congress to "reprimand or remove" federal judges who rule for marriage equality, and at a conservative event in January, he suggested -- jokingly, he claimed -- that same-sex couples who order wedding cakes from bakers who don't approve of their marriages might find poison in those cakes.

Carson's stances have made him a celebrity and a favorite of the far right. But will they make him a candidate? Last month Republican strategist Juleana Glover told MSNBC, "Candidates who would like to see the inside of the West Wing are gonna find a way to be more inclusive on the issue of marriage."

A recent poll shows a record 60 percent of Americans supporting marriage equality. Another poll has indicated that opposition to equal marriage rights is becoming a losing proposition among Republican voters. And support extends to adoption equality, with 80 percent of Democrats, 61 percent of independents, and 51 percent of Republicans supporting adoption rights for gay and lesbian couples, according to a poll from last summer.

The HRC points out that Carson's suggestion that an individual's sexual orientation is a choice is pushed by many right-wing religious groups in order to promote the concept of dangerous "reparative" or "conversion" therapy, a practice that has been outlawed for use on minors in New Jersey, California, and the District of Columbia. There is significant evidence of harm to LGBT people resulting from attempts to change their sexual orientation or gender identity, and all major medical and mental health organizations in the United States condemn the use of reparative therapy.

Carson seems unfazed by criticism of his views and has publicly sworn he won't be stopped by what he called the "P.C. police."

He did cite one area where he felt gays and lesbians should be afforded civil rights -- granting them something like civil unions, although he would exclude them from legal marriages.

"Why do gay people want to get married? Why do they say they want to get married? Because they want to have various rights -- property rights, visitation rights," he told Cuomo. "Why can't any two human beings, I don't care what their sexual orientation is, why can't they have the legal right to do those things? That does not require changing the definition of marriage."

Carson's trajectory from surgeon to Republican presidential aspirant began at the National Prayer Breakfast in 2013. Sitting two seats from President Obama, he launched a rant against Obamacare and the national debt. YouTube clips of those comments boosted him from obscurity to best-selling author and Fox News contributor.

A super PAC, the National Draft Ben Carson for President Coalition, has raised $15 million, according to MSNBC. Watch the CNN interview below.