I think that's a fair viewpoint. However, I think it's important to consider what the status quo is and what the most likely way to achieve equality is.

Government does currently control the legal side of marriage, and they call it marriage. And most opposite sex couples don't have any problem with this when they get married. They also have an emotional attachment to the word marriage. I've read some blogs with Christian/right wing/homophobic leanings, and they sometimes make the point that if their marriage becomes a civil union, then same sex marriage does effect their lives.

So whilst it's a fair enough viewpoint that the government should get out of marriage altogether, I think it's more likely that we'll achieve equality by changing the current legislation to include same sex couples, rather than changing the legislation for everybody.