If true and it really did happened, then the coaches and umpires should have stopped the game and toss those fans out... If they didn't, then I wonder why they didn't do that??? Also, if the kid heard it from the dugout, then the coaches and umpires should have heard it too...
It's one thing to heckle a player, it's another yelling racial slurs...
I've never heckle young kids from coaches pitch to High school, only college and pros...