One thing I don't really get:
This isn't really related to the topic of whether gay marriages should be recognized by the state...
I have trouble with the idea that a gay couple can give a child the kind of upbringing a loving, successful heterosexual marriage can. Aren't we saying, if we say that two men can do just as good of a job, that there is nothing essential or important about the role of a woman and mother in a child's life? That a true mother is unessential and replaceable? Sure, you can honestly love a child just the same as an uncle or cousin or family friend can, but not the unique way a mother can. Neither can you provide mothering if you aren't a mother.
We have already begun to see in the schoolhouses and prisons what, in my opinion, is the effect of most of a generation growing up with partially or totally absent fathers. Do we really want to further the incidence of children growing up without one parent? Will we be well off in the end for this?
This hasn't anything to do with religion, it's the tried and failed formula of half-parenting we are working through in our culture.