The answer is not to push the envelope further, but to restore the primacy of marriage within the law and the culture. Marriage is not something that can be taken lightly, or altered without much impact. Same-sex proponents often point out that some states once banned interracial marriage, but the comparison is invalid. Skin color is inborn and benign, while sexual behavior has everything to do with character, morality and society's basic rules of conduct. Eliminating one entire sex from an institution defined as the bringing together of the two sexes is a quantum leap from eliminating racial discrimination, which did not alter the fundamental character of marriage.
Marriage reflects the natural moral and social law which is in evidence all over the world.
No society has loosened sexual morality outside of man-woman marriage and survived. Analyzing studies of culture spanning several thousands of years on several continents, Harvard sociologist Pitrim Sorokin found that virtually all political revolutions that brought about societal collapse were preceded by a sexual revolution in which marriage and family were devalued. When marriage lost its unique status, women and children most frequently were the direct victims. One can no more expand a definition of marriage than one can expand the definition of a yardstick and still use it as a reliable measure. Marriage-based kinship is essential to stability and continuity.