The question of whether grating rights to the unmarried was brought in a newspaper related to the Opus Dei.

Not surprisingly a lot of people rejected the very idea basing the concept of legal marriage and religious marriage as the same. Others said that if people choose to live without wedding each other no law should de facto marry them. Others dislike putting equal rights to people regardless of their sexual orientation, so a new legal figure should be created to grant homosexual couples legal rights under a special category. Others just depict the move against because the state had to preserve morality and should not make cohabitation legal because it is what majority of the people may think it is right. And others went against the move arguing it stopped short of granting full marriage for homosexual couples, and therefore the only equality is to make same-sex marriage legal being the move itself no more than just a patch-work.

Source: El Opinólogo