Jesus prayed for unity among His people. This is recorded in
John 17. He also said that the way people would know who His disciples are is by their love one for another. This is recorded in
John 13:34-35.
There IS unity among God's people. We have all been placed by His Spirit into His one body. So, positionally we ARE one. In God's sight we ARE one. He only has one body, one bride, one building. But, in a practical, every day real world manner, we are quite divided. We have gathered ourselves into little kingdoms or organizations or religious/political parties and divided up people and scattered His church. Not only has this hindered our effectiveness in working for Him, and presented a grotesque caricature of Him to the world around, I'm sure it grieves Him to see those divisions/organizations/factions among His own.