The confusion lies with the church which no longer teaches the cross through symbols.
Have you considered that Jesus said not to take vows, yet in marriage they take a vow? It is because originally, they were not taking a vow. They were on stage playing the role of Christ and the church. It was preaching the cross through symbols. Christ gave himself for his bride, the church, and his bride obeys and learns from Christ.
A male-male marriage declares men to be equal to God.
A female-female marriage signified that Christ was just a man.
I am happy to perform gay weddings: We are gathered here together to celebrate that these two are in complete rebellion against God according to the ancient symbols of marriage. A proper marriage declares that Christ died for the church who is now bound to him in one flesh. They are fruitful by the fruit of the Spirit and multiplying by teaching. This is at least the second time they have preached the cross through symbols, the first being their baptisms where they declared that they have submitted to the Word of God represented by water and put to death their old natures, and are now living in a new life in the Spirit, having been raised into the air. These have chosen to declare good and evil for themselves, making themselves to be false gods. Let's have cake.
Asking a business to do things that they oppose is asking them to paint a pentagram on their door. Marriage is not just a churchy sentimentality. It is the preaching of the cross, which is the heart of the church.
But it is not hate. When you ask me what is 2+2, I cannot say 5. The haters want to force us to say things that are not true. I will not come into your temple and force you to have a Christian marriage. Nor will I ask that you put symbols of my faith in your business. It is called simple courtesy.