1Jn 2:9 He who says he is in the light, and hates his brother, is in darkness until now.
1Jn 2:10 He who loves his brother abides in the light, and there is no cause for stumbling in him.
1Jn 2:11 But he who hates his brother is in darkness and walks in darkness, and does not know where he is going, because the darkness has blinded his eyes.
Few professing Christians would admit to "hating" their brother – but sometimes we "dislike" other Christians so much we don't want to be in fellowship with them – or maybe even with any Christians!
This is walking in darkness according to John. When Christians truly love and care for one another, and make sacrifices to add value to others in the community, then the people of the world will sit up and take notice – because this is a BRIGHT LIGHT. To live in this light, we need to love one another.
No love for truth will cause us to totally withdraw from fellowship with other Christians. We need to embrace relationships with other believers in order to do the will of God.