It's not a key difference, it's a difference of no consiquence. Context (i.e. when people say that they don't believe in sex before marriage, they invariably mean that they don't condone it, not that they don't believe it occurs) and common sense (i.e. the idea that any adult doesn't believe hook ups at bars actually occur is an absurd idea) make it patently obvious what she meant.
Nit picker. Nit picker.
-Kev
It is a difference of major consequence. For those who actually grasp the language, that is. When I say "I don't believe in Santa Clause", I'm not saying "I don't think Santa Clause is appropriate." I'm saying "HE DOESN'T EXIST!"
When I say, "I don't believe you." I'm not saying that you are innapropriate. I'm saying I don't believe something you have said, done, or in some conveyed to me.
Saying "I don't believe in X" to convey dissaproval isn't even an accepted convention. It's something said by people who haven't had enough education to know better.
Never leave it up to your audience to infer your meaning especially when your language (when misunderstood) might make your audience think "wow.... what a twit."
It's like saying "irregardless" or "I could care less." Or using "they" to refer to a single person of unknown gender. Just because there is a niche of ignorant people who say these things, doesn't make them ok or correct.
This is significantly different form saying "I'll be a monkey's uncle" or "right as rain" even when these statements make no real sense (or at the least, most people don't know what they litteraly mean/meant)... because these are accepted cliches. The previously mentioned phrases are not.