We are a reflection of the people around us at any point in time.
Certain people bring out the best in us as opposed to others. We feel respected, loved and accepted for who we are. Whereas, with others we may simply be a 'friend of convenience'. Yet others make us realize the things that we completely wish to avoid. You need all sorts around you to understand them and more importantly- yourself! There are several shades of grey all mixed up, but some are closer to white and some nearer to black.
Its your intelligence, awareness and life experience that teaches you to be aware of these differences. You cannot cut off any one. You need to learn to maintain the relationship in manner that is most beneficial for you.