I think I get it
Ok, you've heard this part before. Very dark, stylish, etc., so I won't waste much time on this.
However, I think I understood the orgy at the end, and that one girl's shirt.
I'm pretty sure he was trying to show that this "Council" thing was a bunch of teenagers.
Think about it. Popular teens wear stupid shirts like that, listen to music, and fuck eachother.
So thinking of it that way, the end made sense.
As I said, very dark and stylish. Loved it.