It’s just that their solution to this injustice is wrong. If one has identified a religious tenet written into law, the appropriate response isn’t to have the state alter it as it feels necessary. If you’re a libertarian and arguing for that, you need to turn in your libertarian badge (keep the gun, obviously). Having the state fiddle around with religious tenets is a controversial and dangerous action that will have no end. Is anyone really so naive as to think that gay marriage will be the last marriage-based controversy ever? No, there is only one course of action that will actually end this: Marriage and the state need a divorce.
Some may see that solution as cutting the baby in half, but it really just finally restores some sanity to the issue. The state has never been good for marriage, and gay marriage is not the first marriage-law controversy; there have long since been arguments involving things like divorce — arguments often very religious in nature, i.e., the exact sort of arguments you want the state to stay away from. As a Christian, I feel very strongly about the separation of church and state, not as a protection for the state — who cares about the state? — but as a protection for the church. If we can learn one thing from human history, it’s that anything government gets involved in becomes corrupted. And marriage is very important, so it’s something you want to keep the government far away from.
All the government should do is write up a suite of legal contracts between two consenting adults (or groups of consenting adults — let’s just head off that next controversy) that can be signed in front of a lawyer. If you want a religious ceremony and want to call it a marriage, that can be done before or after you sign the legal documents, but the ceremony itself will have no more direct legal consequences than, say, a Catholic confirmation ceremony. And everyone can continue to argue what is considered a proper marriage and what isn’t, but that debate will be moved to the best place for all contentious debates — to a place where it has no legal bearing on anyone.
As you can probably guess, I pretty much agree with this line of reasoning and support it in its entirety. Marriage should be a religious matter, not a political/civil matter. Unfortunately, saying that the government should simply be involved in enforcing legal contracts that happen to coincide with the living arrangement formerly known as marriage is stupid since the government has now shown a tendency to ignore contracts when the contract is disadvantageous to the signatory formerly known as a wife. So, not only should the government not be involved in marriage, it shouldn’t even be involved in contracts.