Have you ever been told by a complete stranger to 'cheer up,' just because you didn't look radiantly happy at the precise second they caught your eye? This guy has the opposite problem. He's got a smile on his face, but because he identifies as an 'emo,' it doesn't suit his look. He wants the world to know he's got a cold, dark, soul, and he can't do that if he can't manage to frown when someone points a camera at him.
From Fridman's response, we now know that if he were an actor, he would definitely take the 'method' route. It's outside Fridman's comprehension that someone could just 'be' sad; they need a reason. Based on this boy's age, he might be heading off to college soon. Those tuition fees will give him something to cry about. His eyes are still full of cheer, though. He's smiling inside!