The people who do the most good in fighting gay marriage are church groups, family advocates, pro-lifers, Christians, and so forth.
The Catholic position is that we should love everyone, and want what’s good for them. That means that you need to love and sympathize with those who are gay—but not gay activities. Hate the sin, but love the sinner. Since gay marriage is not good for gays any more than anyone else, and since it undermines true marriage, family and children, it should be opposed.
But I think it’s perfectly reasonable to say that they are not focused specifically on opposing gay marriage. Their interests are more broadly Christian. In fact, I presume that their leaders continue to oppose it, but their emphasis is on what is good for marriage, family, children—and also for those with gay inclinations.
The opposition is trying to paint them as gay haters. Of course, they deny that, and rightly so.
I hate seeing that quote over and over. When people see "love the sinner" they think it means something like loving your child or loving your spouse or loving your country or holding hands in Sedona, Arizona. It means nothing of the sort. All it means is desiring for that soul not to be lost. None of the ordinary meanings of love were meant to apply. As a Christian you can both hate the sin and find the sinner to be disgusting and repugnant, as long as you pray for his or her soul to be saved. If you have the gift of evangelization you can try that, too, but good luck with that.