Churches are not forced to perform or recognize marriages they do not wish to under the Washington law. But they don't get to dictate to the rest of us what goes on outside of their chapel doors.
Putting same-sex couples in a separate class of civil unions is a version of the "separate but equal" argument in Plessy v. Ferguson. It was later correctly declared unconstitutional.
The only thing that would be separate is the term used to describe it. For me, it's a languge issues, not a civil rights issue. And besides, all laws "discriminate" against somebody.
100% the same or nothing. I'm not sure you realize this, but those are the options. Oh, wait. No. There's only one option: 100% the same.