I think allowing gay couples to marry does strengthen the institution, because it ensures that everyone in a family has access to the same civil rites and rights, and so the heterosexual marriages are as affirmed as effectively as the gay ones. (It is not my experience that the straight siblings and families of gay people feel their marriages affirmed by excluding some of their own.) By removing the incentive for gay people to enter into false straight marriages, which often end in divorce or collapse, wrecked childhoods and betrayed spouses, heterosexual marriage is also strengthened. And the practical alternative to marriage equality - civil unions for straights and gays - presents a marriage-lite option for everyone that clearly does threaten traditional marriage in a way that gay marriage never could.This is a good take on the subject, and quite close to my own, though I would also advocate stricter divorce laws and other mechanisms to increase marriage success rates. I would also argue that any conservative who has the time to argue endlessly against gay marriage probably ought to be spending that time finding ways to save marriage in general--the culture at present is drifting toward marriage failure. Gay marriage likely won't help or hinder that, so long as our society at large, including not only divorce laws, but also cultural attitudes toward marriage and commitment, remains as shallow and hedonistic as it is now.
This is greatly inflamed by the media, which glorifies sex and scoffs at commitment. There's no good way to change this, as we have a lovely little thing in our country known as free speech. However, as I've argued before, redesigning our communities to be more family friendly, walkable, and connected and then localizing and re-valuing our community institutions that teach our kids their values (like schools) could all go a long way toward creating a better value system in this country.
Where are we now, as a civilization? We have forgotten our history. We live between "anything goes" and "who cares?" in a sort of gluttonous apathy, fueled by disconnectedness from our larger family units and a love of materialism. We are not taught that it takes hard work to sustain a marriage. We are not taught that monogamy is natural, and while difficult, the far better approach to relationships. We may be told this, by our parents (so many of whom turn out to be hypocrites) or our pastors (also, lots of hypocrites there...my best friend in high school had a pastor for a dad, and his parents got divorced. In fact, out of all my old friends, my parents are almost the only couple still together...) But being told something and being taught something are not the same.
Without a larger community to fall back on and to be held accountable to, we become nihilistic and detached. I think Pearl S. Buck sums it up:
"The lack of emotional security of our American young people is due, I believe, to their isolation from the larger family unit. No two people - no mere father and mother - as I have often said, are enough to provide emotional security for a child. He needs to feel himself on in a wold of kinfolk, persons of variety in age and temperament, and yet allied to himself by an indissoluble bond which he cannot break if he could, for nature has welded him into it before he was born."Do you see what I mean? We need a wider net. My mom comes from a family of eight siblings, and when I was younger I was constantly surrounded by family. We ended up moving (several times) and as I grew into those restless, rebellious years I had virtually no (extended) family to speak of.
Which led to a great deal of rebellion on my part, I think. It would have been harder to face all my uncles and aunts, cousins, grand parents, etc. than simply my parents. But I didn't have to. We'd cut ourselves off.
So as a society, as conservatives, the point should be finding ways to change the world to enforce family, connectivity, anti-materialism, and love. Gay marriage does no harm to any of these things. If anything, it strengthens society because it incorporates the non-mainstream into the mainstream. It helps settle people down.
More on this later...