We, as Orthodox, Catholic, and Evangelical Christians…
The root of the problem is in the first sentence of the Manhattan Declaration. Think about how you must define Christian in order to sign this document. As for me, I would not ascribe the title of Christian to anyone that rejects the truth that salvation is by grace alone through faith alone in Christ alone. The Roman Catholic Church does just that, they reject this plain truth from the scriptures in favor of their traditions.
It is our duty to proclaim the Gospel of our Lord and Savior Jesus Christ in its fullness, both in season and out of season. May God help us not to fail in that duty.
Well, you did fail in that duty here. The Gospel is not proclaimed. Instead of the Gospel, we are given law as a basis for social action. The declaration sets up a Gospel presentation, but we are given the law instead of Gospel. The law is not the Gospel, the law cannot save only condemn. Part of this problem comes from a group of people who disagree on what the Gospel is, trying to do a good work for the sake of the very Gospel that they disagree about.