There are two class-based killings in Season 5 of Dexter. These killings give us insight into the demographic that supports Dexter. The first killing is the "tearing apart" with an anchor of a guy who says, "Well, your wife can suck my dick." He is ugly and doesn't use language well. He is the class opposite of your well-educated, lower middle class, "my dad was a cop" Dexter.
Dexter needs to fit with whatever demographic downloads it, rents it, buys it, or watched it on HBO the first season. I've relied on Netflix until Season 5, when I turned to one of the free "Watch Dexter Free Online" sites.
So what do we see in the Guy in the Restroom? He insults women, he speaks in a dialect, he sneers, he's not attractive, his clothes don't quite fit him. Yeah, it's ok to kill him. If the viewer is a middle aged woman.
What about the creepy ex-cop who makes use of the video and tapes Dexter showing Lumen how to make a downward kill-thrust? Well, we dislike him because he's crass. The tv show, however, also wants us to dislike him because he is "dogg'ed." This is more difficult. It's only by being persistent that people from the wrong class can work their way into the appropriate sphere.
Upshot -- the viewers of Dexter are "hailed" by this pop cult test into the position of believing it's okay to murder men because they are crass, crude, and tough.
