depends how you define a true believer. i am not christian, but i would claim that the people you describe aren't true believers because they haven't really understood the bible.
Pretty much every religious person believes that THEIR understanding is the correct one. You cant objectively say that "this is the correct understanding" from a religous perspective (you can however do it from a for example a historical or textual analysis perspective).
You cant objectively prove that only mormons or bapists have "understood" the bible correct and everyone else are false believers.
that's my point. everyone has a different idea/interpretation, and thus there is no objective definition of a true believer. GP says that true believers come off as insane. that doesn't sound like a sensible definition for a true believer. iaw. whatever a true believer is, i don't think it's that.
what if jesus already returned? then the true believers would only be those that have recognized his return. there are people who did make that claim. that's who i would investigate.
