Running clock

Week 2 we are blowing a team out. Clock had been running since 5 minutes in to the 2nd half. Losing team was getting chippy. We stop them with about 1:30 left on the clock. White hat hands the ball to umpire and tells him to not to set the ball basically telling everyone the game is over. The white hat hacks the clock at 30 seconds. I'm telling the offense to come off the field and to go to the 50 to shake hands. Sideline official tells me to get off the field. I tell him I don't need to because the game is over. He tells me I need to be off the field incase the offense snaps the ball. I tell him how are we going to snap the ball if the umpire is holding the ball and our team is walking to the 50. He responds does that mean you don't have to listen to me. I look him straight in the eye and tell him that's exactly what it means. He was reaching for his flag as the horn sounded.