The one who says he is in the Light and hates his brother is in the darkness until now. The one who loves his brother abides in the Light and there is no cause for stumbling in him. But the one who hates his brother is in the darkness and walks in the darkness, and does not know where he is going because the darkness has blinded his eyes.
So I know a few church-folk who claim to be Christians yet hold grudges & refuse to reconcile with people. Look at this verse above & see what it says.