Gay Marriage

I saw this attack on gay marriage on Facebook. Since the comment I ended up writing (on FB, rather than the blog) was rather long, I thought I'd share it here too: I have to say I'm not at all convinced. First, marriage is not "the only relationship where children can be conceived and born within the life-long union of their own natural parents", since children can be born out of wedlock and their parents may still stay together. Second, even if this was distinctive to marriage, it would suggest that we need a word not for lifelong union of man and woman but rather lifelong union of man and woman raising their biological children, if that's what's so special. This isn't what marriage means, as the author concedes ("This doesn’t mean that a man and a woman are obliged to have children, or that they are always capable of having children.") These examples apparently don't dilute the meaning of marriage, since it's still the case that marriage 'ordinarily' means lifelong union of man and woman raising their biological children. But, if this is so, then I don't see why gay marriage is any threat, at least provided it's not so common as to change the 'ordinary' case. Then marriage ordinarily means lifelong union of man and woman raising their biological children, or relevantly similar cases, such as childless couples of either sex.