I've never written about gay civil unions on this site, mainly because I don't have a firm opinion. But Rob in the Comments has asked me about civil unions and taking the state out of marriage, so I'll try to articulate my thoughts here.
First, I oppose gay civil unions (and, of course, the oxymoronically-labeled "gay marriages").
Second, I agree the state shouldn't be involved in marriages.
Third, I realize that the result of my second opinion undercuts my first (given their druthers, the United Church of Christ would marry druids to trees).
Here's the thing: The state has injected itself everywhere. It shouldn't be involved in the marriage business, but neither should it be involved in a host of other areas. Too often, "libertarians" are merely people who want the state removed from just one area, which is usually an area in which they have a definite opinion. Many atheists with a self-professed libertarian bent, for instance, want "In God We Trust" removed from coins and the prayer removed from Congress' opening sessions. They think they're being neutral. I say, if you want to be neutral, remove the coins (the state monopoly on them, anyway) and Congress.
I'm not willing to remove marriage from the state until a lot of other things are taken away from the state. If we take away the state's marriage business, we're simply conceding the gay marriage point. Because the state is so huge and pervasive, it can't be silent on an issue without fundamentally altering that issue. That's the problem.
Return to the First Amendment example. If we remove God from government, we're taking God out of the public square because the government is so big. The biggest fallacy among atheists is that, by being silent on God, the government is being neutral. That's simply not true: By being silent, the government is siding with the atheists. I wouldn't really care (and would, if given my choice, want the government silent on religion), but the government is pervasive, making its stance on religion (and the morality that often flows from it) important. I don't want to eliminate religion from the public square. I want to eliminate government from the public square (or at least minimize it to the most radical extent possible).
People say religion causes strife. That's not true, not at all. It wasn't true in the seventeenth century, it's not true now. Government causes strife. Government fought the wars in the seventeenth century, not the churches (sure, religious beliefs played an important role in those wars, but so did a host of other socio-economic-politico factors. And no matter what: The soldiers fought for and were paid by the government.)
Shift to today's political climate: Every (every! I'd love someone to point out an exception; I'm still contemplating these matters so any challenges are appreciated) major public battle, from school prayer to anti-fag t-shirts in the schools to gay marriage to the estate tax, emanates from one group trying to get their way with a branch of government, whether it's the local school board or the Supreme Court. Because government has become so pervasive, it has turned everything it does into a major battle ground.
Across America, people are wringing their hands at the extreme partisanship, the major divide between red and blue. Well, it's because the state is huge. Political contests have become major deals. A lot hinges on them. If your side loses, America is more likely to become a place where you don't want to live. That's because the state now has so much power over America. Every governmental issue is huge. Gone are the days when you could simply ignore the hacks in DC and go on with your life. If you do that, the hacks in DC will be hacking at your life. (Fortunately, people like me can largely ignore the hacks in DC, but that's because I'm letting others fight the ugly fight for me.)
I want the state out of marriage, yes. But I also want the state out of my wallet, my child's education, and my retirement. I want the state out because I want peace. I'm tired of the fighting, and the fighting won't stop until the state shinks like those kids in that Rick Moranis movie. And as long as the state is huge, that's where the battles must be fought, and I'm not willing to concede an inch to the libertine left, whether explicitly (by prohibiting private employers from discriminating against gays) or implicitly (by taking the state out of marriage).