Now I exhort you, brethren, by the name of our Lord Jesus Christ, that you all agree and that there be no divisions among you, but that you be made complete in the same mind and in the same judgment. For I have been informed concerning you, my brethren, by Chloe's people, that there are quarrels among you. Now I mean this, that each one of you is saying, "I am of Paul," and "I of Apollos," and "I of Cephas," and "I of Christ." Has Christ been divided? Paul was not crucified for you, was he? Or were you baptized in the name of Paul? -Paul ( from 1 Corinthians 1:10-13)
The last questions are rhetorical. This means that they have an obvious answer. In this case, the obvious answer to them should be 'no.' What comes to mind when I read this passage is all the denominations of Christianity. Why are we divided?
Disagreement, when done with respect, is extremely healthy. It leads people to be able to agree to disagree. It teaches one to let go of being 'right' for the sake of loving your brother. It also opens your mind and heart to new ideas that may actually be better than your own. The body is supposed to grow together in love. If we all depend on ourselves and the churches that agree with us, we just breed stubbornness in our opinions, which may be wrong. To hear others' views is humbling, and I know we all agree that to be humbled is to be like Christ (Philippians 2). The only thing that matters which we all must agree on is the Gospel. Did Christ die for your sins? Mine too. Now let's be brothers (or sisters).
To disengage with someone because of minor disagreement is to detach from yourself an important part of the body. How can the arm walk without the legs (1 Corinthians 12)? You are losing an important member of Christ. Satan gets a foothold. He will attack the areas of weakness which are absent due to disagreement. For example, if you disagree theologically with someone who has a gift for prayer and let that come between you, you have lost a great opportunity to have a prayer partner and someone to teach you the value of prayer. Satan will attack your prayer life because it is not your gifting. The body works best with all its parts.
Practically, what am I asking on a grand scale? To rally against the churches and demand unification? Not really. But if we each start agreeing to disagree, we could push past our differences to gain those things which truly matter. Love your brother. Welcome disagreement and try to actually understand each other. You may learn something. Stop being stubborn in a way that is unloving. Also, can we just avoid making those who believe in predestination feel like outsiders in some churches? Can we stop making those who believe that humans have complete free will feel stupid in others? Ask yourself: is it worth losing a member of the body to be 'right'?
Recommended Reading on this topic:
Christians Building Unity by Don Knoop (my grandpa)
