I think that the theme of this movie is to understand the consequences of your actions, and to accept responsibility for them. The theme is actively shown in this scene because Jules is directly discussing what he's learned throughout the course of the movie, and that itself is the theme.

The lines in this scene reinforce that the while theme of the movie is being stated here. In this scene Jules is saying how he's learned that he can't let himself be used as a tool for evil men. The lines in the scene tend to point right at his face. The line from his gun forms a path right to his face, as does the line from Bunny's gun. The line form the diner seats also tend to lead back to Jules. The lines, mostly the lines from guns, help to give focus to Jules and in turn focus on what he's saying, as he's giving the whole theme of the movie in this scene. It also leads back to the fact that his shape is in contrast with the rest of the scene. His afro is a very rounded shape compared to the rest of the characters.

The rhythm of the scene also gives importance to what Jules is saying. The rhythm is mostly Jules talking then allowing someone to comment, then coming back to Jules. This rhythm gives even more importance to what Jules is saying, which is important because what he learns is the whole theme of the movie.