Modern marriage came from religious tradition, but the idea of marriage didn't. Some animals have lifelong mates, they are essentially married. Are those animals holding a ceremony in a church? No, but lots of humans do. It is blatant discrimination to not let a certain demographic have that ceremony, in that church. Your argument that marriage is between a man and a a woman has no grounds. There is no reason for it to be like that, besides the fact that it is ingrained in people's minds! You know what else used to be ingrained in people's minds? The earth is flat The sun orbits the earth Africans are lesser beings We proved all these wrong. Marriage doesn't require proof. It is legal, not religious. It is a social law that governs the "sanctity of marriage", and social laws aren't real laws. Open your eyes, there's a reason we have a constitution, and a bill of rights, to prevent legal inequality.