A black lad at my work keeps saying, if for example he asks for a light for cigarette and you don't have one, "It's cos I'm black right?"

He's joking, but he doesn't discriminate as to who might get his tone and who mightn't; I'm not sure if he's aware of how passive aggressively confrontational that can be in some contexts.

I've wondered recently how he'd react if I responded, with the same smile with which he says it, "Actually, yes, it's because you're a ni**er".