The Bishops and the Federal Marriage Amendment

Maggie Gallagher linked to the U.S. Bishops' recent reaffirmation of a statement on marriage as indicating that the Church does not share my misgivings about the Federal Marriage Amendment.  I agree that Church leaders are supportive of the amendment; their statement, however, reflects the difficulty in articulating publicly accessible grounds to oppose the legal recognition of same-sex relationships.  Note that I am not saying that it is impossible to articulate such grounds, but it's difficult, and many attempts to do so either fall flat or resort to divine revelation via sacred texts.  Consider the opening paragraphs of the bishops' statement:

The Catholic Church believes and teaches that marriage is a faithful, exclusive, and lifelong union between one man and one woman, joined as husband and wife in an intimate partnership of life and love. Marriage exists so that the spouses might grow in mutual love and, by the generosity of their love, bring children into the world and serve life fully.

Moreover, we believe the natural institution of marriage has been blessed and elevated by Christ Jesus to the dignity of a sacrament. In this way, the love of husband and wife becomes a living image of the way in which the Lord personally loves his people and is united with them. God is the author of marriage. It is both a relationship of persons and an institution in society. However, it is not just any relationship or simply another institution. We believe that, in the divine plan, marriage has its proper meaning and achieves its purposes.

Therefore, it is our duty as pastors and teachers – a responsibility we share with the Christian faithful and with all persons of good will – to promote, preserve, and protect marriage as it is willed by God, as generations have understood and lived it, and as it has served the common good of society.

Because this statement leads to the conclusion that the Federal Marriage Amendment should be supported by all persons of good will, I'm not sure why it is relevant that "marriage has been blessed and elevated by Christ Jesus to the dignity of a sacrament" or why the model of Christ's love for His Church gives insight into the nature of civil marriage.  These statements by the bishops are not, and should not be, deemed inappropriate arguments in our public discourse, but they do seem unhelpful.  Thoughts?

Rob