God is the greatest champion and example of love. He asks each of us to love our neighbor. Yet, he was very clear that there is a distinct difference between loving our neighbor and having sex with them.
A married man should love his female friend. But if that love moves into a sexual relationship, it is called adultery, which is a serious sin.
Likewise, an unmarried female should love her male co-worker. But if that love moves into a sexual relationship, it is called fornication, which is a serious sin.
Equally, a married or unmarried man should love his male neighbor. But if that love moves into a sexual relationship, it is called homosexuality, which is a serious sin.
In short, sex within marriage is blessed by God; sex outside of marriage is sin.
So why not allow same-sex marriage and avoid this problem altogether? God has purposely defined marriage as being between a man and a woman. That is his intention and his law. No person or government has the authority to redefine a law of God.
Regardless of what Uncle Sam allows, God forbids the related sins of adultery, fornication and homosexuality.