All divisions in the church only hurt the witness we have to share with the world. My guess is not only was Paul concerned with the community of the Church at Corinth, but, being the missionary that he was, he was also concerned what the world would think of the church and what kind of witness it was.
So much of what we do speaks to the world. They really do watch and see how we react to things, how we treat one another and how we treat those outside the church. I can't begin to tell you how many people ask about the split that recently happened in the Episcopal church and is still ongoing. Why does it happen? How do we feel about it? Is St Matthew's going to leave? What is our position?
Divisions in the church really go beyond these questions. When Christians can't even find a way to live in harmony with each other, how do we talk about the love of Christ for all people and "Jesus loves you" with a straight face? Who would believe us when we say these things but at the same time don't live our lives loving our neighbor?
The only way we are ever going to be believable, is to put our divisions aside and just focus on the mission of the gospel of Christ to tell and show the world that God loves them.