This setup serves as the ethical crutch for the audience. We root for Dexter because he cleans up the scum of Miami, but the show constantly asks: Is he a vigilante hero, or is he a monster wearing a mask?
Recent additions to the franchise continue this tradition of sharp writing: Dexter - Season
Start with Season 1. Fall in love with Season 4. Endure Season 6. And absolutely finish with New Blood . This setup serves as the ethical crutch for the audience