While researching the cross, I came upon a great sermon from John Piper in 1998, Christian Unity and the Cross. Drawing from the text of 1 Corinthians 1:10-17, Dr. Piper shows the root causes of the disunity among the people of God. Here is a snippet…
The other reason it's relevant to say that Christ is not divided is that when a believer has Christ, he has ALL of Christ. No one needs to feel inferior or superior if Christ is really your great treasure. Christ is not divided. If you have him, you have all of him. And to have all of Christ is to have everything you need to be happy forever and ever.
I would encourage you to give the text of his sermon a read.
The cross is the great unifier of the people of God. When you strip away the denominations and institutions and factions we have built up, all of the redeemed sheep of Christ are unified by the cross. The cross is our common confession and our common hope. This unity does not negate that we hold certain truths or that we are warned to be wary of false teaching. This unity does not mean that we accept as brothers those who are heretics or that we fail to enforce church discipline in love with an eye toward restoration. What the unity of the cross does mean is that if I start to think of myself as a Baptist or as a Calvinist first, if I exclude others from fellowship because they don’t share my self-identification I put the cross to shame. It matters nothing that we share attendance at Together for the Gospel or that we are “members” of this church or that, or that we have a more nuanced form of theology. What matters is our redemption at the cross. As Dr. Piper states so well, at the heart of all Christian disunity is pride and pride is the antithesis of the cross.