From A Softer World:
First of all, ASW loses points right away for trying way too hard to be 'edgy' or something, here. So the humor is supposed to be that the kid is a violent racist? Aside from that being not-so-funny, it's not worrisome that a kid might enjoy killing hookers in the video game, because they're not, y'know, human beings--instead, they're women, and sluts on top of it. On the other hand, "blacks" (ack) are human, so it's ...funny?