Though he ate with the publican and the sinner, he was their example and he never condoned any sinful act. Light and fellowship work together. Light and darkness cannot share the same space. Not only is darkness devoid of any light but also of love. But he that hates his brother is in darkness, and walks in darkness, and knows not where he goes, because that darkness has blinded his eyes.
Christians have nothing in common with the unbeliever.
We have been transformed we have a new goal and aim in life, which is to please God. With our new spiritual thinking we are to come out from the world and its old ways. We are to take on a new identity and life in Christ and be separated from the past. All things have become new the bible tells us. God desire holiness from his people.