I don't believe teens are seeing through the "transparency" in Christianity as much as they are just passing through a stage of rebellion fueled by aggression and uncertainty mixed in with that whole self-centered invincibility slash personal identity phase in the midst of their often chaotic, misguided, emotionally based lives governed by reduced critical thinking ability, experience and a general lack of knowledge the result of biased information gathering techniques and a poorly indexed, mostly non-relavant, paper-based resource. Asking them for their rational is the easy way of finding out if their decision to be godless related more to their emo-ways than one grounded in reason.
Ones choice in Religion or non has more to do with ones own personality than anything as I see it, so its no surprise the youth today are either not phased by it in the first place or strongly against, as they are with their parents, authority, past fads, homework and everything else. If you view Religion as a club, teens today just don't fit in very easily.