The most effective of all morality-based arguments for same-sex marriage, the one that persuades more people than any other argument, is the one that equates opposition to same-sex marriage with the old opposition to interracial marriage.

The argument, repeated so often that it sounds incontestable, is this: Just as parts of American society once had immoral laws that forbade whites and blacks from marrying, so, today, society continues to have immoral laws forbidding men from marrying men and women from marrying women. And just as decent people overthrew the former, decent people must overthrow the latter.

Thanks in large part to widespread higher education -- the higher the educational level, the more one is likely to hold this view -- vast numbers of Americans believe in this equation of sex (gender) and race.

But the equation is false.

First, there is no comparison between sex and race.

There are enormous differences between men and women, but there are no differences between people of different races. Men and women are inherently different, but blacks and whites (and yellows and browns) are inherently the same. Therefore, any imposed separation by race can never be moral or even rational; on the other hand, separation by sex can be both morally desirable and rational. Separate bathrooms for men and women is moral and rational; separate bathrooms for blacks and whites is not.

The second reason the parallel between opposing same-sex marriage and opposing interracial marriage is invalid is that opposition to marriage between races is a moral aberration while opposition to marrying a person of the same sex is the moral norm. In other words, none of the moral bases of American society, whether religious or secular, opposed interracial marriage -- not Judaism, not Christianity, not Judeo-Christian values, not deism, not humanism, not the Enlightenment. Yes, there were religious and secular individuals who opposed interracial marriage, but by opposing interracial marriage, they were advocating something against all Judeo-Christian and secular norms, all of which saw nothing wrong in members of different races intermarrying (members of different religions was a different matter). Continued...