Anti-Gay Marriage Argument makes no sense

I was bewildered by this LA times article over the weekend describing the latest tactic of the DOMA defenders planning to argue before the Supreme Court, that is, that marriage is necessary for heterosexuals only because of the possibility of accidental child bearing.

Marriage should be limited to unions of a man and a woman because they alone can “produce unplanned and unintended offspring,” opponents of gay marriage have told the Supreme Court.
By contrast, when same-sex couples decide to have children, “substantial advance planning is required,” said Paul D. Clement, a lawyer for House Republicans.
This unusual defense of traditional marriage was set out last week in a pair of opening legal briefs in the two gay marriage cases to be decided by the Supreme Court this spring.

Am I taking crazy pills or does this make absolutely no sense? At the same time, I had just read (via Gawker)
this marriage announcement:

Ada Laurie Bryant and Robert Mitchell Haire were married Saturday in Hockessin, Del. Robert L. Bryant, a Universal Life minister and a son of the bride, officiated at his home.
The bride, 97, is keeping her name. She graduated from Lesley College in Cambridge, Mass.
She is the daughter of the late Ada Lee Laurie and the late Richard Laurie, who lived in Hingham, Mass.

The bride was a widow and the groom a widower.
The couple met in 2007, when Mr. Haire and his first wife, Jean, moved into Country House, a retirement community in Wilmington, Del. Mrs. Bryant had lived there since 2001 with her first husband, Leonard, who died shortly after they moved in. Mrs. Bryant and Mrs. Haire became close friends.

On Jan. 25, 2012, Mr. Haire, a hobbyist poet, slipped a sonnet vowing “friendship and affection” beneath Mrs. Bryant’s apartment door with a note that said “this represents how I feel in our relationship as a couple.” He was afraid to give it to her in person.
“I was desperately trying to strike a balance between too timid or bold. I didn’t want to mess things up,” he said about the courtship. “I can attest that it doesn’t get easier even in advanced age.”

Mrs. Bryant finally accepted his proposal on Aug. 6, and they will move into her apartment (“It’s slightly bigger,” he said) after the wedding.
She explained why she first turned him down. “There’s a great difference in our ages, as you can see,” she said. “I didn’t think it was the thing to do because I don’t have that many years ahead of me, but he said, ‘That’s all the more reason.’ I like him very much. I love him. So we’re going to be married.”

It’s all very sweet, finding love and getting married at even such an advanced age. But by the logic of the DOMA advocates, these two shouldn’t be allowed to marry because there is no chance of offspring.
Can we really defend this law by saying marriage is only for procreation when so many examples abound of how it clearly is not?