Dexter - Serial Killer/Con Man?

I started watching the tv show Dexter earlier this year, and I immediately thought back to it when we started discussing the themes presented in this course. The series is based around Dexter Morgan, a serial killer who follows a certain 'moral' code in that he only kills other serial killers or people he as otherwise verified as 'bad'. If this doesn't twisted enough, Dexter works as a blood spatter analyst from the Miami Metro Police Department. He often analyzes his own crime scenes, or, when the police department fails, takes it into his own vigilante hands to stop the murderer who's crime scenes he has been investigating.
As a child, Dexter's adopted father took notice of his psychopathic tendencies and need to kill, so rather than attempt to address this issue, he taught Dexter how to use this killing 'addiction' for the greater good. He imparted on Dexter a certain code he must employ whenever killing, so that Dexter could only kill bad people, people who didn't deserve to live.
In order to maintain his serial killer lifestyle, Dexter must don a persona of normalcy, portraying himself as an everyday lab geek, husband, brother, and father to the rest of society. This series then brings up obvious issues of lying and a sense of an 'essential self' that we have been discussing throughout the course. Every day of his life Dexter must live out a lie on some senses, hiding the essential part of his being; his need to kill. He lies to everyone around him, but what is the root, the need of this lie? For Dexter, his lying is imperative to his survival; if he wants to avoid a death sentence or spending the rest of his life in jail, this charade must remain in tact. Furthermore, Dexter lies to protect others. He can't bear the idea of his sister, his wife, his co-workers, and his own son, to ever know the truth of his true self. Is then Dexter's lying a positive action? Does it have ultimate roots in morality?
Furthermore, this series brings up important issues of life and its precious value. Dexter acts as a vigilante in many ways, bringing justice to the city, as he sees it, by killing off the murderous scum that don't deserve life. But who is he to evaluate whether they deserve life or not? Is this 'code' that his father imparted on him truly applicable in every possible situation?
If you get a chance to watch this show, I really would, because it really makes one question whether lying is always detrimental, or whether in some instances, like Dexter's, it's perhaps necessary, and for the best.