There are better ways to handle things than exacerbate or worse, sink to their level by beating them with a stick (s). Chances are, if they are still resorting to those B-level "that's so old" racist comments, (and most of them aren't even aimed at the right ethnicity), better to just ignore them, walk away like that boy you were talking about seemed to do.
Sad truth, but reality - in the words of Kanye West (If I butcher these, forgive me). "Racism be happening everywhere, they just be calling it something different."
And honestly, if you REALLY want to do something about it, do it the way that society will actually award and recognize you for it - hop the red tape and take it up to them. B*tching about it won't do much, really.