I am going to let the group chat know that my friend online cheats in this game.
Why are you talking about your friend? Why do you think he cheats at game?
I don't have to prove anything to them.
You shouldn't spread rumors without evidence. Your friend might fight out and be hurt. They could also be reported as cheater if people accuse them.
It's going to be fun watching him get reported and having people hate him for it.
It is wrong to make accusations without any proof. You are really just causing your friend to go through harm just for your own amusement.