Here's the original cartoon: http://www.penny-arcade.com/comic/2010/8/11/
The kerfuffle's in many places; search "dickwolves" if you're curious. Here's the writer's response: On The Matter of Dickwolves http://bit.ly/gZ8UGp
I think the idea that rape jokes promote rape culture is as reasonable as the idea that dead baby jokes promote dead baby culture. But this can't be explained to people who don't understand that in art, what's obvious may not be what is meant.