I know we've talked about it before, but I thought
this article was especially good, because it discusses the history of the specific case, and puts a human face to this. You aren't punishing anyone but the children who are denied permanency, and who have only ever known their (loving) parents.
As someone who works in child protection, and has worked with gay foster parents, I wouldn't even understand the concept of banning gay adoption even if I were heterosexual.