As a reproductive physiologist, I cringe every time I hear or read the statement that marriage should be restricted to one man and one woman. It is high time for all humans, faith-based or not, to shed the shackles clamped around the myth, dating back thousands of years, that gender determination in our species is strictly bipolar. When 1 in 500 births results in an infant innocently born genetically, physiologically and or physically "outside" the established gender norms, it is not possible to formulate nondiscriminatory definitions of "man" or "woman."
Those innocent, yet very silent "outliers," are also God's children who deserve the same rights in a just, tolerant and educated society. Thus, marriage should be defined as a legal union between two humans, period.
Educate yourselves and hopefully these debates, based on a fundamental fallacy, will dissipate. We have far more important issues to resolve.