Replies

John MacArthur and R.C. Sproul strongly disagree with Professor Roebuck.

Disagree on what? MacArthur refused to sign the Manhattan Declaration, saying:

...the document falls far short of identifying the one true and ultimate remedy for all of humanity’s moral ills: the gospel. The gospel is barely mentioned in the Declaration. At one point the statement rightly acknowledges, “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”—and then adds an encouraging wish: “May God help us not to fail in that duty.” Yet the gospel itself is nowhere presented (much less explained) in the document or any of the accompanying literature. Indeed, that would be a practical impossibility because of the contradictory views held by the broad range of signatories regarding what the gospel teaches and what it means to be a Christian...
....the agenda behind the recent flurry of proclamations and moral pronouncements we’ve seen promoting ecumenical co-belligerence is the viewpoint Charles Colson has been championing for more than two decades. (It is not without significance that his name is nearly always at the head of the list of drafters when these statements are issued.) He explained his agenda in his 1994 book The Body, in which he argued that the only truly essential doctrines of authentic Christian truth are those spelled out in the Apostles’ and Nicene creeds. I responded to that argument at length in Reckless Faith.

Likewise, Sproul refused to sign it, saying:

"The Manhattan Declaration confuses common grace and special grace by combining them. While I would march with the bishop of Rome and an Orthodox prelate to resist the slaughter of innocents in the womb, I could never ground that cobelligerency on the assumption that we share a common faith and a unified understanding of the gospel....how could I sign something that confuses the gospel and obscures the very definition of who is and who is not a Christian? I have made this point again and again since the days of ECT [Evangelicals and Catholics Together]. Though the framers of the Manhattan Declaration declaim any connection to ECT, it appears to me that the Manhattan Declaration is inescapably linked to that initiative, which I have strenuously resisted."

Professor Roebuck agrees with them, making the same point in the article here:

Nowhere does the Declaration admit that Protestant, Catholic and Orthodox Christians have fundamental disagreements over just what the Gospel is. The explicit positions of the Declaration concern homosexuality, abortion, euthanasia and religious liberty, issues on which all three of the main streams of Christianity essentially agree. But when it implies that Christendom is in agreement on the Gospel, the Declaration strikes a fundamentally dishonest tone. But we haven't time to tell this tale, important though it be

It's the answer to the question of "is the personal, i.e. individual response to the Gospel enough to reclaim the culture?" that Roebuck uses as the thesis of his article.

One last statement that I think is pertinent to your comment that "John MacArthur and R.C. Sproul strongly disagree with Professor Roebuck":

Those who did not sign the document believe that it is a lamentable example of the confused sort of ecumenical theology, on display in the ECT (Evangelicals and Catholics Together) statements, and that it implicitly commits its signers to acknowledge a commonality between evangelicals, Roman Catholics and Orthodox on the gospel, who is a true Christian and what is a true church. They rightly point out that the Alliance has always been and remains unanimously critical of the presuppositions and products of ECT.
Those who did sign the document believe that it is a statement of solidarity, not of ecumenism, and that it represents the kind of principled co-belligerency advocated by, for instance, Francis Schaeffer and James Boice. These signers believe that document actually helps clarify their concerns with the whole ECT project, because the Manhattan Declaration only asks evangelicals, Catholics and Orthodox to agree on matters on which we actually agree (marriage and sexuality, the sanctity of life, and religious liberty), rather than purporting an agreement in vital matters on which we do not agree (the Gospel, what is a Christian, what is a true Church).
It should be made clear that those Council members who did not sign the document agree with what the document says about the social issues it addresses. Their concern is that the document implies an agreement between evangelicals and Catholics on the Gospel where there is in fact not an agreement. Conversely, those Council members who signed the document fully understand the agreement on the documents' statement on social issues that they share with those who didn't sign, and also fully appreciate the non-signers' concerns for Gospel clarity and fidelity. However, the Council members who signed do not believe that the document commits them to an agreement with Roman Catholics or Eastern Orthodox on the nature of the Gospel, the Church or who is a true Christian.
-- from the thread The Manhattan Declaration: A Statement from Ligon Duncan