Nancy Polikoff is a Left Behinds Reader
OK, so it's also the argument feminists and queer liberationists have been making since at least the 60s. But I think it's the way to go, and Polikoff makes the argument nicely.
Civil unions for all couples acknowledge that there is meaning in the word marriage, and that it has a dark side.
It's reasonable to hope that someday couples seeking a legal status will go to a county building for a civil union, and those seeking a religious status will go to a house of worship. A couple seeking both would make two stops.
Some advocates for gay and lesbian couples in New Jersey are demanding that the Legislature give them marriage, not civil unions, because a separate status for same-sex couples is discrimination. They're right, but it's discrimination that works both ways. Different-sex couples who want recognition for the family they form should be able to reject the word marriage in favor of a phrase with less baggage.
As a commenter at the Notion wrote,
The opponents of same-sex marriage often like to imply that marriage hasn't changed since the late Roman empire, but the facts just don't support that. Marriage is a social institution like any other, and it changes with society no matter who may try to prevent it. ...
... Put the definition of "family" firmly in the hands of the person whose family is being defined, as it should be.