Explain, in a quiet, private discussion, that you're concerned about his outbursts. Many coaches will change their ways when they realize someone is watching. If the coach says he can't control himself, try moving your child to another team. As you might suspect, this is the coach who wants all the players to do everything precisely the way he says to. Most big league ballplayers will tell you that there are many different ways to hit a baseball.
Some batters choke up.
Some take long, looping swings. As long as it works, it's okay. There will be plenty of time in junior high and high school to hone techniques to perfection. At younger ages, it's much more important that kids just enjoy playing the game. Remind the coach that when a child is nine or 10, his individual style of holding a bat or dribbling a soccer ball really doesn't make much difference.