The institution of marriage is legally a state matter, and religious customs -- such as marriage restricted to male and female only -- should not prevail over individual freedom in a secular and multicultural state.
Why? Why should the State do more in civil contracts than make sure they are enforeced? If we are to say that anyone can "marry" anyone, why should the state put all the numerous restrictions and obligations on third parties that are not parties to the contract?
You are just stating a position when you state that "marraige is legally a state matter". For many, many years it was not. No marriage licenses were sold in many states before 1900. I am positing a position that marraige should not be a "state matter".
Please explain why marraige should be a "state matter" and if so, why should not the state restrict it?