We all remember Terminator II, when the Terminator went to the past and told little John Connor that it was his destiny to become the saviour of the human race. John Connor, a normal teenager up to this point is taken by surprise and his whole life changes because of what the Terminator tells him. Hence...Hero John Connor.
Well, perhaps John Connor and Ben Linus have a lot in common. In Little Ben's case, Sayid (a stranger) comes into Ben's life and has a deep profound effect on Ben. Assuming, Ben recovers from the gun show Sayid inflicted on him, he must now come to terms with why he was shot. If he does figure out that Sayid came from the future to kill Ben because Future Ben is evil, then this event could have a self fullfilling prophecy for Ben. "He tried to kill me because I'm going to be evil, therefore I must be evil" Hence...Evil Ben Linus.