Kids who spot bullshit, and the adults who get upset about it
Luckily for me my parents supported my constant questioning of nearly everything.  Neither were very religious, but my mom did go to church and made me go to Sunday school and church.  Eventually I was thrown out of Sunday school for asking too many questions [1], and at that point laid out a pretty good argument why it was a waste of time for me to continue to go to church.  That was the last time I was a part of any organized religion.[1] "The bible says so" is simply not a good enough answer - ever.  To me a much better answer is simply that a person wants something beyond themselves to believe in even though they know they will not ever prove it to be true.  I may disagree with that, but I can respect a person who is honest with themselves.