Teenagers can feel religious longings just as powerfully as they do romantic ones. There is nothing sinister in teens talking in the language of faith. Quite likely Koenig once had similar thoughts—about personal integrity, moral seriousness, responsibility in relationships—just in more abstract and secular (and I would say, less exact) terms.
It’s hard to remember just how hysterical our teenage selves could sound. I realized this a few years back when I stumbled upon an old diary in which I talked about, yes, my faith and relationships. I hardly recognized the voice in those pages, but I also didn’t want to dismiss it. There was something in the passion of my teenage self that I needed to relearn.
Adnan may well be a murderer (the series leaves this fact unresolved). Whether or not he is, there is nothing murderous in his expression of the universal tension between old loyalties and new loves. Serial’s suggestion that talk of sin and the devil might be homicidal is pure prejudice.