—1 John 2:9-11 (NASB)
In 1 John 1:6-7 the first characteristic defining those who "walk in the Light" are those who "practice the truth". This is actually defined there as the true definition of "fellowship". John provides a second characteristic here expanding upon our personal relationships, that someone who "abides in the Light" is someone who "loves his brother". In other words, it's impossible to claim you love the Light and yet by your choices, actions, and/or behavior hate people. And please, don't be silly enough to ask, "Who's my brother?" We already went through that with Cain and Abel, not to mention the Good Samaritan.
If this all sounds funny to you, I'm very seriously happy for you. But I've actually known Christians, in fact even prominent well-known pastors and teachers, who love to preach and expound the truth, but really don't care much for people. I have known leaders who because they think their job and function in the church is the most important thing, actually put distance between themselves and people so they won't be "distracted" or "unnecessarily involved" in things which they describe as "the affairs of others". They seem to have a form of biblical myopia when it comes to personally applying particular Scriptures such as these from John.
Coming to the foot of the cross is only the beginning entrance into the Light; it's supposed to be continued on a path of our own changed behavior measured by the way we treat others. The absence of love for others is the literal and spiritual equivalent of "the darkness". What began with a rejection of sin and an embrace of the truth is supposed to mature into biblical love. The odds are very good that where there's a problem with displaying biblical love lies a problem with sin, or truth, or personal relationships, or all of the above.†††