Well there's the problem right there. The players shouldn't get to pick what team they are on. The league should be responsible for placing players on the correct teams and at the proper level for their skills. If this young man is too developed to play in his own age group, he should be moved forward to a competition level that is appropriate for him.
It is stupid suburban politics, however, I'm sure there is a travel team in the area that would love to have someone with his skill, even if he has to pitch up. Side note, a kid on my son's old football team could pitch faster than that at 9 and he played on a select team with 11 and 12 year olds
He can still play with his friends. But if he wants to play organized sports, he should play with kids at his own level.
On one side this is a good thing, because it just isn't fun for the opposition. However, he's nine years old, he should be allowed to play baseball