The issue is not what you think is moral because you agree it is bad or not, it is the standard of God's word that weighs in as authoritative. It doesn't matter if you don't like gay marriage either. it is the false narrative that one's freedom to sin must be accepted by all. That is not the freedom it is Bondage. Those who call it freedom call evil good and good evil.
They have perverted freedom.
Fine. This is your personally held religious belief. But you would be foolish to demand all people in a secular country based on a constitution to accept this as a legal determiner of rights and freedoms. Do to so would be to alienate such a significant number of them that it might quickly become impossible to make yourself properly heard in a debate about freedom and rights.
How do you imagine that would help manifest your morality in society?