Joseph Backholm, the executive director of the Family Policy Institute of Washington, has likened gay marriage to bloodletting, media watchdog reported.

Backholm also helms Protect Marriage Washington, the coalition of groups working to repeal Washington state's recently approved law legalizing gay marriage in the state.

During an appearance Thursday on The Janet Mefferd Show, Backholm told host Janet Mefferd that marriage equality would eventually be proven “untrue” like the medical practice of bloodletting.

“Redefining marriage in this way, saying that there is no difference between men and women, that it's not important for children to have both a mother and a father, that's not just bad policy, it's wrong in the eternal sense. So because it's untrue, it will ultimately be proven as untrue and we will come around to recognize the error of our ways. We used to believe in bloodletting as good medical practice, culture has embraced a lot of things temporarily until they realized it's based on things that are not true. This is one of those, it has to be temporary, not just because I want it to be temporary, but because it's untrue in the eternal sense.”

Backholm also rejected comparisons between the gay rights movement and the civil rights movement.

“[T]he reason these are different, today's argument about the redefinition of marriage would be like the civil rights movement if the civil rights movement was an attempt to have black people be referred to as white people,” he said.

(Related: Washington gay marriage foes promote claim that gay parents molest their kids.)