I have two classes, Human and Monster.

both have a Property called MoveBehavior

Human has HumanMoveBehavior, and Monster has MonsterMoveBehavior

I want the HumanMoveBehavior to move AWAY from Monsters, and MonsterMoveBehavior to move TOWARD Humans.

The problem I'm having is where should I put my code to move? 

In the Human/Monster class?

Using this approach, I had a Move() Method, which takes a List of all entities in game, decides whether it's a Monster or Human using a method called GetListOfOpponents(List allsprites) and then runs GetNearestOpponent(List opponents);

But this looks really messy.

Should I have a SpriteController that decides where the Sprites move? I'm unsure where I need to put this code :( 

Thanks!