My dad always told me that it was not whether you won or lost it was how you played the game. He meant that I was to treat others with respect. To work as a member of a team. It does not appear that this kid has been taught that by his folks.
All of us have gifted children. Not all are gifted in sports, some are gifted in relationships, academics, other walks of life. It is our responsibility to help them learn to use those gifts for the benefit of others. Not to focus on themselves, but to live a life that builds others up, even as we compete with them.
The sporting arena is a great classroom for that learning. So is the difficult relational landscape of the public school. As parents we need to engage with our kids with this. Their action under pressure will reflect either our equipping them to handle those things well or else will reveal areas where we should have engaged more effectively.