A reader posted my AOL New article on her facebookpage and got this response from a friend:

I see multiple problems with her argument,
1. She does not mention divorce, which has already ‘redefined marriage.’ Divorce rates in our nation have been hovering around 50% for quite some time, and divorce can be very detrimental to children involved.
2. There are some heterosexual couples who are physically unable to bear children. As far as reproduction is concerned, they are in the same category as homosexual couples. Both of theses couples can adopt children, yet no one questions the ‘parental status’ of heterosexual parents who adopt.
3. There are many married couples who choose not to have children, so saying that the ‘essential purpose of marriage is to attach mothers and fathers to their children’ is an exaggeration that remains unsupported by empirical evidence.
4. In some cultures and ethnic groups, marriage rates are decreasing and couples choose to cohabit instead. These groups have already ‘gotten rid of marriage’ and they are not seeing an adverse effects.
I’m more inclined to agree with the comment on the article from Ken, and I’m very glad prop 8 was overruled; however, I do appreciate this woman’s attempt to provide non-religious argument against gay marriage…

I had a limit of 650 words for that column, so obviously I cannot deal with every possible objection. So let me briefly amplify my remarks, mostly to say that I have dealt with many of these issues multiple times.
1. On divorce. I write about divorce regularly. In fact, divorce was one of the first issues that got me into the study of marriage and family. I have a couple of recent podcasts, here and here. My books, Love and Economics, and Smart Sex, both deal with the whole range of marital breakdowns, without ever once refering to same sex marriage. Both books are available at the Ruth Store.
2. There is no need for family courts to redefine parenthood due to the existence of infertile married couples.
treating same sex couples as equivalent to opposite sex couples requires the law to switch from a “presumption of paternity” to a “presumptiion of parentage.” SSM advocates treat this as a small deal, but it is actually a huge shift. I discuss this in this brief video.
3. the married couples who are childless by choice require a separate argument that I have not developed yet.
4. It is quite true that cohabiting is the chief alternative to marriage throughout the Western world right now. However it is completely incorrect to say that they are seeing no adverse effects. Again, I written about this multiple times. Here and here are a couple of podcasts.
I hope this helps your friend, Claire!