Defend from WHAT, Exactly?

I'm not up in arms about the Catholic Church's position on Gay Marriage. I'd have to be painfully naive not to have expected them to hold exactly the official position they hold. I'm not even shocked or outraged by their attempts to bully secular political authorities. Again, hardly unexpected.

But, when this translates back into secular politics -- and it will, of course, with blinding speed -- I promise you that a phrase you're going to hear a lot is, "Defense of Marriage."

The Federal Law in support of this bigotry is, you'll recall, called "The Defense of Marriage Act." And each and every person I've ever heard speaking out against the rights of gays to marry has invoked the desparate need to "Defend Traditional Marriage."

So that leads me inexorably to a very important question...

Defend from WHAT, exactly?

Are there homosexual brute squads roaming the countryside, waiting for the legalization of gay marriage to force straights to marry members of their own sex?

Is there some data I'm unaware of that shows that if people weren't shackled by laws limiting their spousal opportunities exclusively to the opposite sex, people would just abandon the whole heterosexual thing, marry within their own genders in droves?

Did I miss a meeting?

See, personally, I'm married to a member of a Gender Not My Own, and like it that way. Even were I legally allowed to marry into my own gender, I really can't see that I'd do so. Yes, the vast improvement in my sense of style and home decor is tempting, but not enough to get me to abandon the pleasures of being married to someone with all those fun bits that I and other guys lack. (Although, as I grow older while continuing to be obese, I can simulate a couple to a greater and greater extent. Never mind, Sharing Violation!)

And I can't help but think that the vast majority of Heterosexuals agree with me. And I can't help but think that we like-minded heterosexuals are in the vast majority. The darwinian logic alone is inescapable.

So can someone, anyone, please tell me what "Traditional Marriage" needs to be defended from?

Many thanks!