>contemporary political issue

You have every right to your opinion, but Latter-day Saints believe marriage is an eternal and sacred commitment, not a "contemporary political issue." Hence their interest.

>By staying in their church, Mormons explicitly endorse their churches actions and stances

I completely agree.

>...the LDS church can and will inject itself and its considerable demographic and monetary clout directly and voluminously into any political debate that takes its fancy

I wouldn't doubt it. I can even tell you what political debates will take it's fancy: those involving religious issues.

I'll even toss out another idea: it has every right to do so. When you say "the LDS church" what you're really saying is "every member that belongs to the LDS church." Those members have every right to participate in the democratic process, and the "leaders" of the LDS church have as much right to preach their viewpoint to their members as the man in the commercial on TV.

>You can stay and support the actions of your church leaders, or you can leave.

Again, we're totally in agreement here. Even more-so in the Mormon church than any other, since twice a year we have a world-wide meeting where every member has a chance to *literally* raise their hand in support or disagreement with church leaders--watch it online, you'll see the actual hand-raise.

For what it's worth, I think the reason this topic is so difficult to discuss is because there's so little data to go on. I think the LDS church is concerned about the long-term effects on society, but obviously there's been no studies done.

There's no good analogy, but consider it like proposing legalizing off-shore drilling before doing environmental studies, while what little data you have shows what you consider a lot of negative effects.