r-PSen. Gordon Smith (R-Or.), no enemy of gay rights, has apologized for comparing same-sex marriage to the polygamy practiced by his Mormon forebears. Last week he walked into this minefield for reasons of the heart, not the head.

The reaction from the GLBT community was not positive. As the Portland Oregonian reported:

“Talking about polygamy and same-sex unions in the same breath — on the face it’s offensive,” said Frank Dixon, a Democratic Party and gay rights activist. “Maybe he can explain his way out of it.”

Here’s the explanation. Back in the 19th century, Mormons were attacked–driven out of the Midwest, their prophet murdered–in substantial measure because their practice of polygamy violated prevailing Protestant religious norms. The principal opposition to same-sex marriage today is religious as well–just ask James Dobson or the U.S. Conference of Catholic Bishops. Peculiar logic aside (how do you support states’ rights by voting for a federal Defense of Marriage Act?), Smith seems to wish that majoritarian religion butt out, and let particular communities, be they fundamentalist Mormons or gays and lesbians, do their own marital thing. That’s not equating same-sex marriage and polygamy, it’s pluralism.