Fox News host Megyn Kelly defended Johns Hopkins University neurosurgery professor and right-wing media darling Ben Carson's statement linking marriage equality to bestiality by claiming that Supreme Court Justice Sonia Sotomayor made similar comments during oral arguments in the Proposition 8 case, ignoring the broader context of the exchange. 

From the March 29 edition of America Live, Kelly said: 

But [Carson] is not alone in making comparisons to groups. I mean, when you say, who outside of a man and woman would want to be together? There's not a long list. You struggle to sort of find a group outside of gays and lesbians, and even Justice Sotomayor on the Supreme Court this week, Dan, was asking about would it open the door to polygamy, to incest being allowed. Now gays have gotten very upset before when people compare gay marriage to incestual  relationships or polygamist marriages. So did he do something so far afield from what Justice Sotomayor, a Barack Obama appointee on the bench, did in open court this week?

Kelly was referring to an interchange between Justice Sotomayor and counsel for same-sex couples challenging Proposition 8, California's same-sex marriage ban, during oral arguments in Hollingsworth v. Perry on March 26.  Kelly's attempt to tie Carson's degrading statement to Justice Sotomayor is misleading.  In fact, Justice Sotomayor challenged Proposition 8 supporters' positions. 

For example, she asked Charles Cooper, counsel for the Proposition 8 proponents, whether he could name any reason - outside of marriage - “for a State using sexual orientation as a factor in denying homosexuals benefits or imposing burdens on them.” When Cooper relied that he could not, Sotomayor followed up:

All right. If that -- if that is true, then why aren't they a class? If they're a class that makes any other discrimination improper, irrational, then why aren't we treating them as a class for this one thing? Are you saying that the interest of marriage is so much more compelling than any other interest as they could have? 

In spite of this, Kelly seized upon an exchange between Justice Sotomayor asked Ted Olson, counsel for the plaintiffs, to imply that the Justice, who was appointed by President Obama, shares Carson's opinion that marriage equality could be a “slippery slope” to a parade of horribles:

SOTOMAYOR: Mr. Olson, the bottom line that you're being asked -- and -- and it is one that I'm interested in the answer: If you say that marriage is a fundamental right, what State restrictions could ever exist? Meaning, what State restrictions with respect to the number of people, with respect to - that could get married -- the incest laws, the mother and child, assuming that they are the age -- I can -- I can accept that the State has probably an overbearing interest on -- on protecting a child until they're of age to marry, but what's left?

OLSON: Well, you've said -- you've said in the cases decided by this Court that the polygamy issue, multiple marriages raises questions about exploitation, abuse, patriarchy, issues with respect to taxes, inheritance, child custody, it is an entirely different thing. And if you -- if a State prohibits polygamy, it's prohibiting conduct. If it prohibits gay and lesbian citizens from getting married, it is prohibiting their exercise of a right based upon their status. [[It's selecting them as a class, as you described in the Romer case and as you described in the Lawrence case and in other cases, you're picking out a group of individuals to deny them the freedom that you've said is fundamental, important and vital in this society, and it has status and stature, as you pointed out in the VMI case. There's a -- there's a different - (TR p. 47)

Justice Sotomayor did not challenge him further.

Kelly also failed to acknowledge that Justice Sotomayor was not the one who introduced this line of questioning to the Proposition 8 litigation.  Proponents of Proposition 8 included it in their defense of the law:  

Extending marriage to same-sex couples could increase the social acceptability of other alternative forms of intimate relationships, such as polygamy or polyamory."

[...]

Extending marriages to same-sex couples would increase the likelihood that the recognition as marriages of other alternative forms of intimate relationships, such as polyamory or polygamy, will become a judicially enforceable legal entitlement. 

The proponents' Supreme Court brief warned that marriage equality could erode the meaning of marriage, and that "[t]he process of deinstitutionalization could even culminate .... in 'the fading away of marriage,' to the point that it becomes 'just one of many kinds of interpersonal romantic relationships.'

The parties who supported Proposition 8 as amici curiae explicitly warned of a slippery slope to polygamy:

The Conference of Catholic Bishops' brief stated:  

Though no party to this litigation argues that multiple friendships and polygamous relationships constitute marriage, it is not evident why they would not also qualify as “marriages” under the Ninth Circuit's novel test.  Moreover, if the meaning of marriage is so malleable and indeterminate as to embrace all “lifelong and committed” relationships, then marriage simply collapses as a coherent legal category.  

And a brief filed on behalf of 19 states argued:  

Once the natural limits that inhere in the relationship between a man and a woman can no longer sustain the definition of marriage, the conclusion that follows is that any grouping of adults would have an equal claim to marriage. See, e.g., Jonathan Turley, One Big, Happy Polygamous Family, NY Times, July 21, 2011 at A27.

Proposition 8 supporters also raised the specter of polygamy in their campaign to pass the constitutional amendment in 2010.

Early in the Supreme Court arguments, Cooper asserted  that marriage equality would “redefin[e]” marriage and result in harm.

Further, Justice Antonin Scalia has repeatedly raised this argument to support his position that the Constitution does not bar discrimination against LGBT people or even protect them from being imprisoned for their relationships - which he could use to persuade justices with a less firm position on the case.  The justices will consider all of the arguments put forth and the responses to them.

For example, in his  dissenting opinion in Romer v. Evans, in which the Court struck down Colorado's  law barring legislative, executive, or judicial action that protects persons based on “homosexual, lesbian, or bixexual orientation, conduct, practices or relationships,”  Scalia wrote (emphasis added): 

First, as to its eminent reasonableness. The Court's opinion contains grim, disapproving hints that Coloradans have been guilty of “animus” or “animosity” toward homosexuality, as though that has been established as Unamerican. Of course it is our moral heritage that one should not hate any human being or class of human beings. But I had thought that one could consider certain conduct reprehensible--murder, for example, or polygamy, or cruelty to animals--and could exhibit even “animus” toward such conduct. Surely that is the only sort of “animus” at issue here: moral disapproval of homosexual conduct, the same sort of moral disapproval that produced the centuries old criminal laws that we held constitutional in Bowers. 

                [...]

But there is a much closer analogy, one that involves precisely the effort by the majority of citizens to preserve its view of sexual morality statewide, against the efforts of a geographically concentrated and politically powerful minority to undermine it. The constitutions of the States of Arizona, Idaho, New Mexico, Oklahoma, and Utah to this day contain provisions stating that polygamy is “forever prohibited.” See Ariz. Const., Art. XX, par. 2; Idaho Const., Art. I, §4; N. M. Const., Art. XXI, §1; Okla. Const., Art. I, §2; Utah Const., Art. III, §1. Polygamists, and those who have a polygamous “orientation,” have been “singled out” by these provisions for much more severe treatment than merely denial of favored status; and that treatment can only be changed by achieving amendment of the state constitutions. The Court's disposition today suggests that these provisions are unconstitutional, and that polygamy must be permitted in these States on a state legislated, or perhaps even local option, basis--unless, of course, polygamists for some reason have fewer constitutional rights than homosexuals. 

                [...]

The Court's stern disapproval of “animosity” towards homosexuality might be compared with what an earlier Court (including the revered Justices Harlan and Bradley) said in Murphy v. Ramsey, 114 U.S. 15 (1885), rejecting a constitutional challenge to a United States statute that denied the franchise in federal territories to those who engaged in polygamous cohabitation.  

Scalia again parroted the right-wing parade of horribles message in his dissent from the 2003 Lawrence v. Texas decision, in which the Court struck down a criminal ban on consensual intimate sexual conduct:

State laws against bigamy, same-sex marriage, adult incest, prostitution, masturbation, adultery, fornication, bestiality, and obscenity are likewise sustainable only in light of Bowers' validation of laws based on moral choices. Every single one of these laws is called into question by today's decision;

                [...]

The Texas statute undeniably seeks to further the belief of its citizens that certain forms of sexual behavior are “immoral and unacceptable,” Bowers, supra, at 196-the same interest furthered by criminal laws against fornication, bigamy, adultery, adult incest, bestiality, and obscenity.

Scalia has not restricted this rhetoric to his legal writings.  In a December 2012 appearance at Princeton University, a student asked Scalia to defend the language in his Romer and Lawrence dissents.  Scalia responded “if we cannot have moral feelings against homosexuality, can we have it against murder?  Can we have it against other things?” In defending his statement, Scalia denied that he was comparing homosexuality to murder.  He further stated:

I don't apologize for the things I raised. I'm not comparing homosexuality to murder. I'm comparing the principle that a society may not adopt moral sanctions, moral views, against certain conduct. I'm comparing that with respect to murder and that with respect to homosexuality.

Seen in the context of a nearly two-hour oral argument with a long trial record and dozens of amicus briefs, it is unreasonable to suggest that Justice Sotomayor's question demonstrates that she agrees with Carson. 

Carson's comments have been widely criticized, and even Carson, as Kelly noted, has attempted to walk back his comments.