But why does the law need to say it, especially if it were to provide for equivalent civil-union rights?
I see this being put forward a lot and I am still confused by it. The equivalent question goes unanswered: If the two states of affair (marriage/civil-union) are legally equivalent, why should the law give them two different names?
I hear hopeless linguistic pleas to tradition and stuff, but given the fact that language usage changes that kind of argument seems hopeless.