In “Political Liberty: Who Needs it?”, I wrote:

Imagine that in our culture, or in the human race in general, we tended to associate being given a red scarf by one’s government as a mark of membership and status. You are not fully in your national club until you get your scarf.

Now, suppose the government gives red scarves to everyone, except homosexuals. Homosexuals would rightly be upset—they would rightly claim that the government’s refusal to grant them red scarves shows that homosexuals are considered second-class, inferior people. The government’s behavior would tend to induce people (including homosexuals themselves) to regard homosexuals as having low status… Homosexuals and their sympathetic allies would have reason to take to the streets and demand that homosexuals be granted scarves.

(Note: I was discussing the value of voting rights rather than marriage.)

I don’t advocate having the government distribute red scarves in order to signal status. That’s not the business the government should be in.

However, if the government did distribute scarves as a way of signaling status and membership, I’d want it to do so equally. I’d be outraged if it excluded homosexuals, or blacks, or whomever, even though I think it’s dumb for the government to issue scarves in the first place.

I don’t want trivialize marriage. In the case above, the value of getting a red scarf is purely symbolic. The value of having government accept and recognize your marriage contract is not purely symbolic.

Now, it’s an interesting question whether government should recognize marriage contracts, and on what terms it should do so. But given that it does in fact recognize certain marriage contracts between opposite-sex consenting adults, it would need compelling justification not to recognize otherwise identical marriage contracts between same-sex consenting adults.

Going back to the hypothetical world above where red scarves are used to indicate status: Suppose, in that world, that Abrahamic churches, mosques, and synagogues also had a long tradition of distributing red scarves when a person became an adult. Suppose many Americans received a red scarf from their church at the same time that they received it from government. Suppose most of those churches refused to issues scarves to homosexuals because they regarded homosexual sexual activity as inherently sinful.

If the government then began to issue scarves to homosexuals, that would not be an assault on the churches or their members’ freedom. After all, it would not thereby be requiring the churches to issue such scarves. It would not intervene in the churches at all. Rather, this would be a case of a religious institution and a political institution running in parallel. Changing the latter is not the same as changing the former.

For the same reason, if the government changes the civil institution of marriage, that is not the same thing as changing the religious institution. If the government allows homosexuals to marry in civil ceremonies, it does not thereby impose anything on churches.

Ah, but don’t these use the word “marriage” in both cases? Sure, but we can all recognize that there is marriage-sub-civil and marriage-sub-religious. In the eyes of the Catholic Church, I am not married-sub-religious, but I am married-sub-civil.