Legislatures sometimes do some really irrational things. And sometimes, they or other groups in society prompt the populace as a whole to do some irrational things. And that's one of the reasons we have federal courts in this country: to review such actions to determine whether they are rational or irrational in light of the law of this land.
Specifically, a law that discriminates against a certain class of society must, at the very least, be rationally connected to a legitimate government purpose. If the law fails that test, then it is unconstitutional and must be struck down.
Case in point: Kitchen v. Herbert, the case that resulted in several Utah laws being struck down as unconstitutional, including Amendment 3 to Utah's state constitution (which I'll refer to collectively as the "Traditional Marriage Laws").
Another case in point that followed on the heels of Kitchen was Bishop et al v. Oklahoma et al, in which Federal District Court Judge Terence Kern ruled that Oklahoma's constitutional amendment banning same-sex marriage was also unconstitutional.
The States of Utah and Oklahoma (the latter's interests represented by Tulsa County Clerk) were each obliged to defend these laws by, among other things, proving to the court that there is a rational connection between refusing to permit or recognize same-sex marriages and legitimate government purposes.
We're going to hear a lot about rational connections and legitimate government purposes in the months ahead as Kitchen v. Herbert and Bishop climb the appellate food chain (the 10th Circuit Court of Appeal will hear each case), perhaps all the way to the Supreme Court. So, I think it's worth taking a look at some of the "legitimate government purposes" that Utah claims justifies its Traditional Marriage Laws, claims that were echoed in the Bishop case.
Let's speak some truth here: Though the State of Utah and Anti-Marriage Equality advocates like to talk about preserving traditional marriage and the welfare of children - lots and lots of talk about the welfare of children - the bottom line is that these arguments (sometimes thinly veiled) are an attempt to hide the real reason they are against marriage equality, i.e., they believe homosexuality is immoral.
In his decision, Judge Kern in Bishop addressed the line of argument that the State has a rational interest in restricting marriage to heterosexual couples because homosexual behavior is immoral.
“The Court recognizes,” he wrote, “that moral disapproval often stems from deeply held religious convictions … However, moral disapproval of homosexuals as a class, or same-sex marriage as a practice, is not a permissible justification for a law.” Quoting from the landmark decision of the Supreme Court in Lawrence (a decision which ruled that states cannot criminalize consensual gay sex), Judge Kern points out that “the fact that the governing majority in a State has traditionally viewed a particular practice as immoral is not a sufficient reason for upholding a law prohibiting the practice.”
In Kitchen, Judge Shelby addresses this point by quoting from Justice Scalia in Lawrence when he wrote, “‘preserving the traditional institution of marriage’ is just a kinder way of describing the State’s moral disapproval of same- sex couples.” And from another Supreme Court case, Shelby takes another quote when he writes, "'[While] [p]rivate biases may be outside the reach of the law, . . . the law cannot, directly or indirectly, give them effect' at the expense of a disfavored group’s constitutional rights." [Palmore v. Sidoti]
Preserving the Traditional Definition of Marriage
Another favorite of Anti-Marriage Equality advocates is the proposition that preserving the traditional definition of marriage is itself a legitimate state interest.
Judge Shelby deals with this argument in Kitchen by quoting from Supreme Court precedent to note that "tradition alone cannot form a rational basis for a law": "[N]either the antiquity of a practice nor the fact of steadfast legislative and judicial adherence to it through the centuries insulates it from constitutional attack" [Williams v. Illinois], and “[a]ncient lineage of a legal concept does not give it immunity from attack for lacking a rational basis.” [Heller v. Doe].
In Kitchen, the State of Utah advanced the argument that “[t]raditional marriage with its accompanying governmental benefits provides an incentive for opposite-sex couples to commit together to form  a stable family in which their planned, and especially unplanned, biological children may be raised.”
Judge Shelby dealt with that argument as follows:
"The State has presented no evidence that the number of opposite-sex couples choosing to marry each other is likely to be affected in any way by the ability of same-sex couples to marry. Indeed, it defies reason to conclude that allowing same-sex couples to marry will diminish the example that married opposite-sex couples set for their unmarried counterparts. Both opposite-sex and same-sex couples model the formation of committed, exclusive relationships, and both establish families based on mutual love and support. If there is any connection between same-sex marriage and responsible procreation, the relationship is likely to be the opposite of what the State suggests. Because Amendment 3 does not currently permit same-sex couples to engage in sexual activity within a marriage, the State reinforces a norm that sexual activity may take place outside the marriage relationship."
Judge Kern in Bishop expressed similar sentiments:
[T]here is no rational link between excluding same-sex couples from marriage and the goals of encouraging “responsible procreation” among the “naturally procreative” and/or steering the “naturally procreative” toward marriage. If a same-sex couple is capable of having a child with or without a marriage relationship, and the articulated state goal is to reduce children born outside of a marital relationship, the challenged exclusion hinders rather than promotes that goal."
Optimal Child Rearing
Utah and Oklahoma both advanced arguments the State has an interest in "optimal child rearing" and that a prohibition of same-sex marriages advances this interest. Neither Judge Shelby nor Judge Kern were convinced.
"There is no reason to believe that Amendment 3 has any effect on the choices of couples to have or raise children, whether they are opposite-sex couples or same-sex couples … If anything, the State’s prohibition of same-sex marriage detracts from the State’s goal of promoting optimal environments for children. The State does not contest the Plaintiffs’ assertion that roughly 3,000 children are currently being raised by same-sex couples in Utah. These children are also worthy of the State’s protection, yet Amendment 3 harms them for the same reasons that the Supreme Court [in Windsor] found that DOMA harmed the children of same-sex couples. Amendment 3 'humiliates  thousands of children now being raised by same-sex couples.' ... Utah’s prohibition of same-sex marriage [also] further injures the children of both opposite-sex and same-sex couples who themselves are gay or lesbian, and who will grow up with the knowledge that the State does not believe they are as capable of creating a family as their heterosexual friends."
Judge Kern, in Bishop:
"The Court assumes, for purposes of this motion for summary judgment only, that (1) the “ideal” environment for children must include opposite-sex, married, biological parents, and (2) that “promoting”this ideal is a legitimate state interest. Again, however, the question remains whether exclusion of same-sex couples promotes this interest, or is simply a guise for singling out same-sex couples for different treatment due to “moral disapproval” of a same-sex household with children. Smith [Oklahoma] has not articulated, and the Court cannot discern, a single way that excluding same-sex couples from marriage will “promote” this “ideal” child-rearing environment."
Proceeding With Caution: Negative Impact
In Kitchen, Utah contended that it has "a legitimate interest in proceeding with caution when considering expanding marriage to encompass same-sex couples." But Judge Shelby ruled that the State was not able to cite any evidence to justify its fears.
Similarly, in Bishop, the State argued that avoiding a redefinition of marriage that would “necessarily change the institution and could have serious unintended consequences.” Judge Kern dealt with this argument as follows:
"The 'negative impact' argument is impermissibly tied to moral disapproval of same-sex couples as a class of Oklahoma citizens. All of these perceived 'threats' are to one view of the marriage institution – a view that is bound up in procreation, one morally “ideal” parenting model, and sexual fidelity. However, civil marriage in Oklahoma is not an institution with “moral” requirements for any other group of citizens.
"[The Tulsa County Clerk] does not ask a couple if they intend to be faithful to one another, if they intend to procreate, or if they would someday consider divorce, thereby potentially leaving their child to be raised in a single-parent home. With respect to marriage licenses, the State has already opened the courthouse doors to opposite-sex couples without any moral, procreative, parenting, or fidelity requirements. Exclusion of just one class of citizens from receiving a marriage license based upon the perceived “threat” they pose to the marital institution is, at bottom, an arbitrary exclusion based upon the majority’s disapproval of the defined class. It is also insulting to same-sex couples, who are human beings capable of forming loving, committed, enduring relationships."
That last sentence is a perfect way to end this post: The gist and effect of all of the arguments advanced by so-called "traditional marriage" advocates can be summed up as follows:
"Exclusion of [gays and lesbians] from receiving a marriage license ... is insulting to same-sex couples, who are human beings capable of forming loving, committed, enduring relationships."