I think the issue is that as long as the state endows rights to religious practice (marriage) there is a problem.

If the state only gave rights and taxed civil unions, the churches cannot, by definition, control if other people get married. All they'd need to do is find a church willing to marry them, or start their own.

To quote from another of my posts: --- I think once the legal implications are removed, churches would lose their control over the word by default. It doesn't have meaning outside of the church at that point, and the government "shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof" So if gay people wanted to get married, no one could stop them.