Ben Carson, a retired pediatric neurosurgeon, announced on Tuesday that he is forming an exploratory committee and considering throwing his hat into the 2016 Republican Presidential Primary. In one of his first interviews as a potential candidate, however, Carson told CNN’s Chris Cuomo that he believes being gay is a choice. While this isn’t a new justification for denying same-sex couples rights, Carson’s reasoning for it—that prison sex proves people have control over their sexual orientation—is a somewhat novel spin on an old offensive argument.

Carson explained that, in his view, states should individually legislate the issue of same-sex marriage. Even if states passed discriminatory laws, Carson said, it would not necessarily be a violation of equal protection because people have control over their sexuality. When asked if being gay was a choice, Carson said “Absolutely.” He went on to give what he sees as proof:

A lot of people who go into prison, go into prison straight but when they come out they’re gay. So did something happen while they were in there, ask yourself that question.

Carson then used this to justify a system in which same-sex couples would be entitled to everything but marriage.

Late Wednesday evening, Carson apologized for his comments, saying that his words did not reflect his “true heart” on gay issues. In a statement, Carson said: “I do not pretend to know how every individual came to their sexual orientation. I regret that my words to express that concept were hurtful and divisive. For that I apologize unreservedly to all that were offended.” Yet even in his apology, he argued there’s no definitive research to say that sexual orientation is not a choice: “Some of our brightest minds have looked at this debate, and up until this point there have been no definitive studies that people are born into a specific sexuality.”  

Though he clearly regrets them after the fact, Carson’s remarks—and even his apology—still show a disturbing level of misunderstanding about sexual orientation that is very dangerous when combined with his willingness to discriminate against same-sex couples. Our discussions about marriage equality have come so far since even the last presidential election; it’s unfortunate that Carson would take such a giant leap backward on his very first day in the field of hopefuls.

Perhaps now, while he is reflecting on his first major foot-in-the-mouth moment of the upcoming campaign, would be a good time to provide a quick lesson on sexual orientation and explain to Carson why his remarks were offensive on so many additional levels.

So here’s some 101-level reminders: Sexual orientation refers to a person’s physical and emotional attraction to others. And it is about far more than just whom a person has sex with. It also has to do with sexual fantasies, emotional attachments, and lifestyle preferences. Moreover, it’s not always an either/or situation; people are not necessarily exclusively heterosexual or exclusively homosexual. As sex researcher Alfred Kinsey wrote in 1948, “The world is not to be divided into sheep and goats … The living world is a continuum in each and every one of its aspects.”

Most importantly, though, sexual orientation is an identity that each person gets to decide for themselves. And the bottom line when it comes to dealing with Carson’s argument is that regardless of their past or present sexual behavior, every person (prisoners included) can identify as gay, straight, or something else. It’s up to them.

Carson himself admitted Wednesday night that it was not up to him to label others’ sexualities. But the second half of his prison argument may be even worse—because he concluded that prison sex means a man has chosen to be gay. Overall, research on prison sex has been scarce; inmates are often wary of telling the truth, for fear of retribution. However, we do know that a lot of the sex that takes place in prison is non-consensual or coercive, and that rape is common. A 2012 Justice Department report, for example, found that nearly one in ten inmates in state prisons, local jails, and post-release treatment centers suffer sexual abuse while incarcerated, at the hands of both fellow prisoners and facility staff. Even consensual prison sex is more complicated than it might be under other circumstances, and decisions to engage in it likely take into account far more than the gender of the other person.

Prison sex is a serious human rights issue and bringing it up in relation to gay marriage shows a lack of understanding about sexual orientation, consent, and human rights. The existence of prison sex cannot be used to prove that homosexuality is a choice; it can only be used as a proof that our prison system is failing.

There’s also the fact that Carson is, according to most scientific and medical studies, just plain wrong about whether sexual orientation is biologically predetermined. A 1991 study published in the journal Science, for example, found that one section of the hypothalamus (a part of the brain which controls sex hormones), is bigger in heterosexual men than in gay men. Other brain studies have found that the brains of homosexual men and heterosexual women are more symmetrical than in heterosexual men and homosexual women. Research has also focused on the corpus callosum—which connects the two halves of the brain—with varying results.

In my mind, however, these studies, and the others done on genetic explanations for sexual orientation, don’t actually matter. Whether or not orientation is biologically determined or a “choice,” everyone deserves access to the same rights—and the only time anyone brings up the debate is when they are trying to advocate homophobic practices, such as “reformative therapy” or discriminatory policies against LGBT individuals.

And that’s exactly what Carson is still using this argument for: discriminating against marriage equality. In the interview with Cuomo, he said it was fine for a same-sex couple to seek the legal rights and property benefits that come with marriage—but marriage itself should be saved for one man and one woman.

Despite his assertions of fairness, this position shows Carson’s willingness to treat same-sex couples as second class citizens. After all, few people accuse heterosexual couple of getting married just so they can file joint taxes come April 15. Heterosexual couples are said to be marrying for love, commitment, or a desire to start a family. This may be news to Carson, but same-sex couples have the same motivations and deserve the same respect.  

Offering rights short of marriage to same-sex couples is a position that politicians on both sides of the aisle were espousing not that long ago. Thankfully, though, many have now come around and evidently realized that “separate but equal” is never truly equal. Today, 37 states allow marriage equality as a result of laws or court rulings, and the U.S. Supreme Court has struck down the Defense of Marriage Act. The Court is expected to give a ruling on the matter by the end of the summer.

Carson’s first day in the field, however, should remind us that bigotry and homophobia are not gone from our country’s politics, and that the struggle for LGBTQ rights will not end if and when we secure marriage equality rights in every state. People face prejudice based on their sexual orientation on a daily basis and some states are even attempting to legalize discrimination against LGBTQ individuals in the name of religious freedom. This is not the time to be complacent—and it’s not the time for candidates who display such clear homophobia.