If, in fact, the "brownie" reference was totally non-racial in nature and the kid just freaked out about nothing, I put that on the kid's parents and upbringing. What is he or she being taught at home that would cause him or her to react in that way?
Going in a different direction: Suppose this nine-year-old actually DID make some stupid, nine-year-old joke that made some reference to a brown-skinned classmate. I find it highly unlikely that this would have happened, but let's say for the sake of argument that it did. "Hey, John, this brownie looks like you" - whatever. That kind of thing would at an absolute maximum call for a meeting with the two kids' parents and certainly a talk from the principal regarding inappropriate jokes of that nature. Encourage the kids to hug it out and move on.