The key to preventing adult misbehavior in youth sports is a youth sports culture in which all involved "Honor the Game." Honoring the Game gets to the ROOTS of the matter and involves respect for the Rules, Opponents, Officials, Teammates and one's Self. You don't bend the rules to win. You understand that a worthy opponent is a gift that forces you to play to your highest potential. You show respect for officials even when you disagree. You refuse to do anything that embarrasses your team. You live up to your own standards even if others don't.
Here are ways that coaches can create a positive youth sports culture so that children will have fun and learn positive character traits to last a lifetime.
Model Honoring the Game in behavior and language, especially when the official makes a "bad" call against your team.
Tell your players you expect them to Honor the Game regardless of what the other team does.
Recognize that you are the leader of the team, which includes the players AND their parents. Set and reinforce expectations for parent behavior in
a pre-season letter to parents
a parent meeting at the beginning of season
pre-game conversations at every game
Support the officials, especially if your parents yell at them. Tell parents they are to Honor the Game even if the official makes a bad call.
Appoint a team parent as "Culture Keeper" to gently remind other parents on the sideline to Honor the Game.