1 Corinthians 1:11-13, NAS: 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?
1 Corinthians 1:11-13, Pete's Paraphrase: Brothers and sisters in Christ, I hear some of you bicker among yourselves! For example, some of you say, "I am of Rome," and "I of Luther," and "I of Calvin," and "I of Wesley," and "I of Pentecost," and "I have the Spirit's Gifts," and "I of THE Church of Christ." Has Christ's Body been been dismembered into independent pieces? Luther was not crucified for you, was he? Or were you baptized in the name of Calvin? Do you pray to the Spirit's Gifts?
There are boundaries - e.g. Hebrews 11:6, John 14:6 - but why can't Christian believers of different backgrounds work and fellowship with each other? We're all going to be spending eternity with each other, so why wait till then to learn to get along? Why not take away one of the excuses non-believers use for avoiding Christianity?