Dealing with Screaming Stubborn Kid

So today i watched this movie, Le Passe. There was a scene where this kid was screaming and on throwing tantrum. So, i thought, what would i do if he was my kid? I think of every possibilities, but looking at how critical the boy was, i concluded, hmmm, i will blackmail him. LOL.. Its very wrong. I know.

So, this guy went to the boy and close the door. He didn't let anyone enter the room except him and the boy and start slow talking with him. It worked! He asked, why and go deeper and deeper into the conversation. The boy changed 360 degree. He was calm and no more problem. So, the conclusion is:

1. NEVER BLACKMAIL YOUR KID
2. BE CALM, AND START A CONVERSATION