Reminder: Parents are not allowed to enter the dugout during games (unless there is a medical need only).
If a parent has a baseball related concern, they should approach the manager after the game away from all other parents and children and address it then. During gameplay the manager's attention is focused on the entire team and the gameplay.
If they still have a concern not addressed by the manager, they can escalate to the commissioner of that division, the league player agent, or league president.