Negative comments towards the players have no place on the field or on the sidelines. He earned the right to coach the game. Your team could end up being penalized by the referee if you coach from the sideline. Any parent who is coaching from the opposing team's side of the field may be removed from the field and cause their team to be penalized. No one is allowed to stay behind the goal lines.
Referees are also volunteers, They're in it for the kids and to have fun.
The coach, the parents and the referees are in it as a team. Negative comments towards the referees have no place on the field or on the sidelines. Parents and coaches must provide a sports environment for players that is free of drugs, tobacco, and alcohol. Use of these products on or around the premises is not allowed and will not be tolerated. Support the kids with positive encouragement but keep your technical coaching to a minimum, the game is for the kids to implement what you taught them during practice.