You're question is old, however I will answer it anyway. Because question. The pale man is a child murderer, so yeah he is evil. In the movie he sits at a huge table topped to the brim with food. If Ofelia, the protagonist of the story, eats any of the food, he will stick his eyes into the palms of his hands and then will eat her. Because.... reasons.
Don't worry, I've had that happen to me. Someone drew a Necromorph from dead Space and I didn't recognize it.
Well, Pan's Labyrinth is a film, but oh well Yep, Ofelia's task is to get something from the room, and she hasn't eaten for a day, so she eats one measly grape and the Pale Man is 'I'mma eat yo face!'. So yeah, if you don't eat anything he won't kill you. But my God is that scene tense.