He that saith he is in the light, and hateth his brother, is in darkness even until now.
One cannot claim to be a Christian and HATE other people. It simply is the same example of a fountain that cannot bring forth sweet water and bitter water from the same fountain... The two do not mix....
this is yet again the GREAT Apostle JOHN writing another tell tale test as to wheter someone is really a believer of Jesus or NOT..