“Because it will bring the wrath of Almighty God down on our heads. “
What part of “Congress shall make no law respecting an establishment of religion” do you not understand?
You’re ignorant of the characteristics of marriage. Not only is it a spiritual union in the eyes of God, it is the fundamental contract that forms the first building blocks of human civilization, civil government, civil law, and economy.
Citing the mythical separation of church and state in this context is even sillier than the usual use of that myth.