You may call your religion beautiful and moderate, but if it reduces some people to second-class citizens by refusing them full marriage equality, then your religion is a problem for society, causing many people to feel rejected and hated.
I know there are problems with extreme beliefs leading to terrorism and violence, but there is also a very widespread problem with supposedly moderate religions institutionalising prejudice. I used to think that this was not a serious problem until I watched a performance of a play about 'Proposition 8', in which a mother said "no girl dreams of being a civil partner".
That's true - why should the dreams of children who want to think of themselves as being fully accepted and respected members of family and society be crushed? Why should a child be told that he or she is second-rate, that their love isn't as real, isn't equal? That institutionalised lack of equality can and does lead to bullying of children, and worse.
A moral religion should not collude with such rejection, should not enable such hatred. It should teach that all are equal, that loving a member of your own sex is as wonderful and as true as the love between a man and a woman. Even this atheist accept that that would be a beautiful thing for a religion to do.