I slapped a 15 yr old kid for playing a game
Why did you slap someone over a game?
I've been playing this game for two years. He is ruining my fun by using a cheat that gives him unlimited health and money.
Even if someone is cheating you have no right to harm them physically. It is a crime to attack someone and hit them especially a kid.
Why can't I do whatever I feel like?
In life we can't just do what we want, especially if it involves assault of a child. Maybe you can play in a different group without him.