This is fair.
Every year when I was in high school, rumors swriled over upcoming food fights. Special assemblies would be held specifically to tell kids "if you do this, there will be consequences". Every year, they did it anyway. When some were suspended, it was always the same: "It was just a food fight, I didn't do anything!". Those kids need to grow up. They got a taste of what would happen if they randomly decided to fling food at strangers in a restaurant. They can't live in their protective, little bubble forever.