Christianity Today is wrong concerning the breakup of the mainline. Their article argues that the unity the NT calls for is found in the commonality across denominations. "Nothing in John 17 nor the rest of Scripture suggests that oneness demands institutional unity." But it's primarily through institutions that one is in a position to live together, impact and influence one another.
And if the only people who are doing that are those that fully agree with us, then we have no one who is in a position to question and challenge us. And it is primarily through such differences that God is able to expand our sense of the world and each other. Otherwise we've just created a mutual affirmation society
Groups in society are based on such a premise. They have a list of common beliefs they organize around. But supposedly the church is different. In the church, God calls us, so that what we share is a mutual calling to live together, to respond to God. The phrase the Disciples use, "No Creed but Christ" takes shape in such an account.
It's not that we don't have creeds or even common beliefs, but it's not the principle of the church nor the basis of union, ideally. Rather it's God's saving work in Christ that provides the bonds of affection. The church is different from the society, ideally, because it calls all of us with the amazing breadth of differences to the same table.
What makes for effective societal groups in the end makes for a lousy church. In Christianity Today's vision the church becomes just another place to find those that will agree with us, like any other group, feeding into the balkanization which seems to define our world today. I don't think that is the vision of unity found within the NT.
I do agree that if people depise one another, it is not possible to live together. But it's a tragedy, not a good or a movement of God that we could be in that place. There's no point in "forcing" people to live together who can't. But what if it's possible to imagine that the other has something to teach us about God? I think we'd be in a better starting place then where CT would have us be.