I think they may have been trying to show "what exactly are we hoping to save?" in addition to making some sort of symbolism point.
 To me Zion seemed a tad cultish. If this was the desired effect, then I can see how the rave scene fits in. I suppose it (along with a few other minor details) will have to be revealed in the final movie.
_________________________
-Jeff
Rome did not create a great empire by having meetings; they did it by killing all those who opposed them.