No, not that kind of "racist joke." It seems every middle schooler must say "YOU RACIST!" to his friends whenever possible.
"You're afraid of the dark? YOU RACIST!" and so on.
Oddly, it seems black children do this exact same thing. It seems to me rathermuch like the old "yo mama" jokes which aren't really meant to be insulting your actual mother. You get cred for making the most clever "yo mama" joke with your friends.
I've talked with my boys about how they don't want to participate in this silliness, even though I don't think anyone means any harm by it.