A witness at the Prop 8 trial testified that gay marriage threatens straight marriage because straight people have already screwed it up.

David Blankenhorn, president of the Institute for American Values, a private think tank in New York, took the stand as the second and final expert witness for the defense in the federal trial challenging California’s ban on same-sex marriage. Lawyers for Proposition 8’s sponsors are trying to prove the voter-approved measure serves a legitimate public purpose.

“If we move toward a widespread adoption of same-sex marriage, I believe the effect will be to significantly further and in some respects culminate the process of the deinstitutionalization of marriage,” Blankenhorn said.

Blankenhorn acknowledged that heterosexuals were responsible for rising divorce and out-of-wedlock birth rates, but said allowing gays to marry could accelerate the process and possibly lead to the legalization of polygamy.

“The man-woman customary basis for marriage in turn reinforces limiting marriage to two,” he said. “If you knock out one of those pillars, the other becomes less comprehensible and therefore less defensible.”

Hmm. So because heterosexuals can’t keep their own marriages intact, gays shouldn’t be allowed to get married? How does Mr. Blankenhorn know this? He read it somewhere.

David Boies, one of the lead lawyers for the two same-sex couples who sued to overturn Proposition 8, tried to discredit Blankenhorn by getting him to acknowledge that he has conducted no independent research on same-sex marriage and his only advanced degree is in comparative labor history.

“I have not engaged in a scientific study were I find data and write up an article that would be published of that nature,” Blankenhorn said. “I have read articles and had conversations with people and tried to be an informed person about it, and that really has been the extent of it.”

In spite of that “expert” testimony, who’s to say that gay marriages can’t be a stabilizing force for marriage? After all the stigma and prejudice they already face, a gay couple could be a role model for straight couples by showing that they can keep a commitment in spite of adversity. Gay marriage could be the best thing that could happen to marriage for everyone, including men and women who marry each other.

Or it could just be another logical step forward in the progress of human and social interaction.