The estimable Tobias Haller has a lengthy post about the arguments going back and forth in advance of GC to which I direct you. He points out that a distinction between the two views of marriage is that one "side" views marriage as an institution, while the other looks at individual marriages as real examples. Certainly, this is often the case in arguments with anti-equality folks. They REFUSE to acknowledge that they are talking about real people and real lives.
Thus, Tobias writes,
The TF [Task Force on Marriage] made this point in its overall thrust towards focusing on the moral values that make a particular marriage holy, rather than in what might make marriage holy as an institution....and
This comes to a head in the discussion of procreation, which appears to be, for many, the stumbling block. From the TF perspective, procreation can be understood as a purpose or good or end of marriage as an institution but need not be understood as such for an actual or particular marriage, and may be an impossibility for any number of specific actual marriages. It seems glaringly obvious to the TF that procreation can take place apart from marriage, and marriage from procreation. It is fine to say, as we have, joining the consensus of the church, that procreation should take place within marriage, but we have rejected the valuation of any given marriage as somehow being less than marriage when the couple do not, or cannot procreate.
The fact that procreation is ideally a purpose for the institution or establishment of marriage has absolutely no impact on the fact of the a real couple's marriage being fully a marriage, whether they procreate or not.Amen, brother.
In any case, for those who persistently argue that the pro-equality side "hasn't done the theology", Tobias's essay and the resources to which he links will be of great help.