You all might like reading what the CA Supreme Court Judges actually ruled in their decision to strike the "marriage is only between a man and a woman" statute. It is awesome to read and handy to reference if someone confronts you about it.
Here are a few important extracts (in quotes).
1. Calling same-sex relationships by another name than marriage impinges on right to marry:
"One of the core elements of the right to establish an officially recognized family that is embodied in the California constitutional right to marry is a couple’s right to have their family relationship accorded dignity and respect equal to that accorded other officially recognized families, and assigning a different designation for the family relationship of same-sex couples while reserving the historic designation of “marriage” exclusively for opposite-sex couples poses at least a serious risk of denying the family relationship of same-sex couples such equal dignity and respect. We therefore conclude that although the provisions of the current domestic partnership legislation afford same-sex couples most of the substantive elements embodied in the constitutional right to marry, the current California statutes nonetheless must be viewed as potentially impinging upon a same-sex couple’s constitutional right to marry under the California Constitution."
2. On finding that there is no compelling state interest in treating opposite-sex and same-sex couples differently:
"Under the strict scrutiny standard, unlike the rational basis standard, in order to demonstrate the constitutional validity of a challenged statutory classification the state must establish (1) that the state interest intended to be served by the differential treatment not only is a constitutionally legitimate interest, but is a compelling state interest, and (2) that the differential treatment not only is reasonably related to but is necessary to serve that compelling state interest. Applying this standard to the statutory classification here at issue, we conclude that the purpose underlying differential treatment of opposite-sex and same-sex couples embodied in California’s current marriage statutes — the interest in retaining the traditional and well-established definition of marriage — cannot properly be viewed as a compelling state interest for purposes of the equal protection clause, or as necessary to serve such an interest."
3. Their reasons were many, but the last seems most compelling:
"Finally, retaining the designation of marriage exclusively for opposite-sex couples and providing only a separate and distinct designation for same-sex couples may well have the effect of perpetuating a more general premise — now emphatically rejected by this state — that gay individuals and same-sex couples are in some respects “second-class citizens” who may, under the law, be treated differently from, and less favorably than, heterosexual individuals or opposite-sex couples. Under these circumstances, we cannot find that retention of the traditional definition of marriage constitutes a compelling state interest. Accordingly, we conclude that to the extent the current California statutory provisions limit marriage to opposite-sex couples, these statutes are unconstitutional."
In my humble opinion, these (along with the rest of the ruling) present clear legal moral reasons why Prop 8 needs to fail, and why civil unions are an insufficient substitute.