I googled "same-sex conception" and found lots of my own posts on other blogs, where I have tried to introduce the bloggers to issue of same-sex conception, usually to no avail. These arguments are all pretty similar, you might want to read some of them to see how they usually end up with the other person "bowing out".
Balkinization (and an old one here)
Blue Mass Group (and here and here)
Alas, A Blog
Creative Destruction (and here and here)
Marriage Debate (Maggie has refused to talk about same-sex conception)
Greater Boston Blog
Althouse Blog (and her only response here)