By one Spirit we were all baptised into one body." 1 Corinthians 12:13 NAS
Mark Twain joked about putting a dog and cat together in a cage to see how they'd get along. They did fine so he added a bird, a pig and a goat. They all did well until he added a Baptist, a Presbyterian and a Catholic - and soon there wasn't a living thing left! Seriously, there's nothing Satan enjoys more than causing division by pitting Christian against Christian, often over insignificant issues.
Notice, before His crucifixion Jesus didn't pray for His disciples to stay loyal or dedicated. No, He prayed that they'd remain united in their love for one another: "That they all may be one, as You… are in Me, and I in You… that the world may believe" (John 17:21 NKJV). Jesus recognised the fallacy of claiming to love God without loving your brothers and sisters. He knew that the church can't fulfil its mission of reaching the lost if its members are at one another's throat. Listen: "The members of the body, though they are many, are one… For by one Spirit we were all baptised into one body." Jesus puts it another way: "Love one another. In the same way I loved you… This is how everyone will recognise that you are My disciples" (John 13:34-35 TM). If we have the right doctrine but the wrong attitude, we'll alienate the very people we hope to attract. A divided, confused world can only be reached by united, loving Christians!