I think that scene kindof adds to the overall feel of the movie.
One of the things I love about that movie is it takes a preconcieved plot line and spins it out of control. The Butch story is the best example. When butch left his apartment, it’s really all you expect of the story, but then you have him running into Marcelus, the street shootout, a fucked up redneck, and fucked up cop. Every step you take to an even more fucked up and disturbing world. That’s why the rape scene is inthere, to just raise the stakes that much more. Besides Marsellus getting raped, and basically being saved by Butch makes his deal with butch seem very resonable, where as it may not have seemed that way without it.
Beside what’s the big deal, you don’t see anything. And let’s face it and big powerful black man being raped by a skinny white cop is a fuckin’ hilarious image, it just doesn’t happen.