John 13:35 "By this all will know that you are My disciples, if you have love for one another."
Why can't genuine Christians get along? Sometimes the problem is their backgrounds.
Some people go deeply into "outward" sin. They'll use drugs, get drunk, serve prison time, have a divorce or two, and then get saved. These Christians then have a greater tendency to go into outward sin. They sometimes have a harder time becoming successful pastors and teachers. They have difficulty with traditional music, and they have a problem with "standards." They also realize that they need a close walk with God, they appreciate what Jesus did for them, and they win spiritual victories over sin that most other Christians never have. They are "doubly redeemed": they are saved from sin and delivered from an evil lifestyle. They understand people better, and they do well at bringing unsaved people to church. And they have a real problem understanding "conservative fundamentalists."
Conservative fundamentalist Christians were usually better-behaved before getting saved. They understand the importance of holiness, and they are willing to obey man-made rules about music, clothing, and other standards because they fear getting trapped by sin. They have a harder time dealing with people, but their devotion to the Word of God helps them become better teachers and pastors. Unlike the Pharisees, they really do care about people, and this group produces many of Christianity's best soul-winners. They tend to confuse "numbers" with God's blessings, yet are hostile to other types of Christians whom God blesses with big numbers. They have difficulty realizing that God can bless Christians who do not act like them. They regard "doubly redeemed" Christians as "carnal" or "worldly," because they do not understand how much the first group has grown spiritually.
A lot of the hurts that Christians get are due to a lack of understanding between two groups of people who are actually trying to live Godly lives.