Essentially, Emily Stimpson of CatholicVote says it all. Civil marriage, with its misdirected focus on the individuals rather than the family formed, looks nothing like what scripture or even history describes. No-fault divorce and the “contraceptive mentality” that marriage is solely directed to the happiness of the individuals and happens to involve one man and one women characterize civil marriage. Christian marriage is a lifelong union of one man and one woman for the purpose of forming a family, to generate and educate the next generation of the Church. Every aspect of Christian marriage, from the components of the institution to its indissolubility to the Catholic prohibitions on artificial contraception is directed to the good of the family.
The pro-marriage advocates would have me believe that civil marriage need not reflect Christian marriage to be worthy of my support. However, I’m really not seeing any significant similarities between the two aside from composition. To argue that allowing “gay marriages” amounts to a redefinition of traditional marriage might be technically sound. But at this point, the gulf between the legal definition of marriage and the objectively true definition is so vast it is really hard to summon any enthusiasm for its defense. It’s not good and evil, it’s twisted and completely twisted.
On the other hand, the abortion abolition movement is about white and black, good and evil, light and darkness, literally life and death. If we had a Second Civil War to decide the issue (God forbid), this is a cause I would gladly die for. Preventing tweaks to an already ravaged definition of marriage? Not so much.