Going back to your view that "these churches should also resign from acting as legal registrars", I think that this is not necessary, the reason being that whatever one's orientation, sexual activity is not necessary for an individual's survival, and therefore it is not wrong to form a judgment on the morality of homosexual activity. Churches are therefore at liberty to refrain from marrying same-sex couples; it is right that they continue to act as legal registrars, however, because heterosexual marriage is the foundation of human survival as a whole.