Ian Ayres & Jennifer Gerarda Brown

In Gay Pride parades across the country this month, the powerful images of straight mothers and fathers marching with their gay sons and daughters continue to elicit huge applause.

These simple expressions of support remain important. But a heterosexual perspective on gay rights can also illuminate other harms of sexual orientation discrimination that are often overlooked.

For example, as heterosexuals, it is easier for us to see the ways in which the exclusion of gay couples from marriage is actually weakening the private and social demands for legal commitments.

This reduced demand for heterosexual marriage can most clearly be seen in the small but growing group of heterosexuals who refuse to marry now because of discrimination. You can search long and hard without finding a heterosexual couple who refuses to marry in Massachusetts because the state legalized gay marriage. But you can find different-sexed couples who refuse to marry in other states where gay friends and family members cannot. Just google the phrase “hetero holdouts.”

It’s increasingly embarrassing (outside of Massachusetts) to invite gay friends to come celebrate your marriage. The Ethicist column in the New York Times Sunday Magazine has responded to readers struggling with the question of whether it’s moral to take a marriage benefit that is invidiously denied others. Some people don’t want to drink from a whites-only water fountain.

Our own Episcopal parish has joined other churches across the country in declining to marry heterosexual couples in a world where same-sex couples cannot.

Marriage discrimination is making it ethically harder for heterosexuals to marry.

Defining marriage literally in terms of gender is increasingly out of step with aspirations that many heterosexual couples have for their relationships. Many heterosexual couples would resist the notion that there is a clearly defined role for one partner based on the fact that she’s a woman, and a distinct role for the other partner based upon the fact that he’s a man. But this is the off-putting assumption that underlies a requirement that marriage must include one man and one woman.

The lack of marriage equality has also eroded societal demands for legal commitments. Employers increasingly are allowing same-sex and heterosexual couples to qualify for benefits if they merely claim to be domestic partners. They think it’s unfair to deny same-sex couples these benefits in a world where they can’t marry; and next they conclude that it’s unfair to deny unmarried heterosexual couples these benefits in a world where unmarried same-sex couples qualify.

This dilution of the demand for marriage is not just occurring at the employer level. Ian still remembers in college how his parents decided to let his sister and her sweetheart spend the night together – even though his parents wouldn’t let Ian and his girlfriend sleep together in the parents’ home.

His dad justified the distinction based on the law’s marriage discrimination. You see, Ian could have gotten married and gained the right to sleep together with his wife. But Ian’s sister is a lesbian and in a world with legal discrimination, it would be unfair to hold Ian’s sister to the marriage standard.

It wasn’t long, however, before Ian’s parents were relaxing the marriage rule with regard to Ian too. In a world of marriage discrimination, it’s harder for society to demand that anyone make a legal commitment.

Ending the state’s marriage discrimination would make it easier for employers (and parents) to restrict benefits to couples who were legally committed – instead of diluting the qualifications to mere protestations of being “serious.”

By ending marriage discrimination, Massachusetts has let its employers go back to the old days, when a “significant other” could only qualify for additional benefits if he or she was legally married to an employee.

Finally, the heterosexual harms of marriage discrimination can be seen in the aftermath of marriages between closeted gay men and women and their heterosexual partners. Last year’s “Far From Heaven” dramatized how the lives of a heterosexual spouse and her children were ravaged when a gay husband came out of the closet and ended his marriage. That movie was set in the 1950’s, but the injury of the marriage closet still occurs and the legal prohibition of same-sex marriage is a big reason.

James Dobson has said that same sex marriage licenses are “really death certificates for the institution of marriage”

But a funny thing happened in Massachusetts last year. More heterosexuals got married. That’s right, in 2000 only 37,000 marriages occurred. But in the 12 months since same-sex marriage became legal, more than 40,000 different-sex couples wed.

The central harms of marriage discrimination are visited upon same-sex couples. But increasingly a legislator who cared only about strengthening heterosexual marriage should support marriage equality.