The Crux of the Prop8 defense.

From the Christian Science Monitor article on the Prop8 case:

“The media should be focusing on the absence of harm demonstrated at trial by the Pro-8 side," [UC Irvine Law School professor Tony Smith] says. "The witnesses for them conceded that same-sex marriage doesn't harm heterosexual couples in any way, and that the ban on same-sex marriages directly harms families,” says Mr. Smith. “Given that over 36,000 gay and lesbians got married in California in the brief period when it was legal, if harm occurs from same-sex marriages, the appellants should have been able to demonstrate it.”