Can a Catholic be "for" it--gay marriage that is?
After Megan's post on the Colbert-Kmiec interview, it's worth pointing out that Kmiec isn't the first Catholic to argue that Catholics shouldn't oppose civil recognition for same-sex couples, carefully distinguishing them from their religious counterparts. Marquette theologian Father Bryan Massingale wrote an interesting guest opinion for the Archdiocese of Milwaukee's Catholic Herald  in 2006, which now-Archbishop of New York, Timothy Dolan, allowed to be printed.
In the piece Massingale argued that an anti-gay marriage amendment to Wisconsin's constitution violated Catholic social teaching because it went beyond restricting marriage to heterosexual couples but also nullified any other civil arrangement, which would be an unjust infringement on the civil and human rights of a specific group of people. Massingale, interestingly, appealed to the arguments of then-Archbishop of San Francisco William Levada (now prefect of the Congregation of the Doctrine of the Faith) when Levada was required to extend benefits to the domestic partners of Catholic Church employees.
It seems clear that same-sex couples are going to continue to win civil recognition for their relationships, with public and legal opinion moving strongly in their favor. The recent moves in Iowa and Vermont, and pending legislation in New York State, are only the beginning. Rather than invest energy into what is surely a losing and destructive battle, it makes more sense for church leadership to put resources into helping Catholics understand (and better live) the sacrament of matrimony than preventing same-sex couples from access to state family law.
This conversation about this issue, like abortion, seems to easily degenerate into a shouting match, so, as always, charity first in your comments.