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...but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin (1st John 1:7, NASB, emphasis mine).

Walking in the Light doesn't eliminate the differences between people, but it does transcend them. Our relationships with other Christians is maintained by the Light we walk in.

Our relations with people outside of Christ will certainly be strained if we walk in the Light, because those who hate God will also hate His children, just as Jesus said.

And it is also true that no Christian walks perfectly in the Light - thus our fellowship with one another will not be what it should be until our final deliverance from the corruption of the world and the flesh is done, in the resurrection.