The recent "protest" involving a mock marriage in Notre Dame in which one person pretended to be a priest[1] seems rather revealing to me. It seems clear from this that they are in fact not simply pushing for the civil benefits. They want something more. They want us to say that their behavior is acceptable. They want us not just to say "whatever works for you," but to say "yes, we agree that your behavior is good." Otherwise a civil ceremony would suffice. Otherwise they would not want it to be in a Church, but would rather reject the Church. But they know that the Church teaches the Truth, and that if the Church were to condone their "marriage," then it would only then truly be one.
This in turn reveals something for the rest of us. In their quest not just for tolerance but for acceptance and endorsement, the homosexual lobby has provided evidence of the case for absolute truth. Because only in the presence of absolute truth does it matter that the Church disapproves of their behavior. Only in the presence of absolute truth would you need, or care about, your marital status in the eyes of the Church as well as in the eyes of the civil law.
[1] http://www.catholicnewsagency.com/new.php?n=4084