Who's the best Christian? The guy with the biggest church? The one who wins the most souls to Christ? The one who reads the most Bible? The one who holds important leadership positions?
Jesus said "By this shall all men know that you are my disciples, if you have love one for another." Christians who constantly war against other saints are not Jesus' disciples. Christians who feel called to expose the sins of groups they disagree with are not disciples. Christians who slander their way to leadership positions are not disciples.
But don't we need to do certain things in order to please God? When you don't love the brethren, any blessing God gives you looks like an attack on your Christian enemies. Any failure you have is a comfort to your Christian enemies.
Also, it is hard to submit to the authority, or to help the ministry, of a Christian enemy. By fighting, you cut off many areas of service where God could use you. That's why God tells us "Above all things, have fervent charity among yourselves."