I wouldn't dismiss it entirely. My teo brothers don't know a thing about Christianity. During the 6 year period between my birth and my brother's birth, my mom kind of went atheist. So where I was given somewhat of a religious upbringing (not really though), my brothers don't know a thing.
They're in high school now, so they clearly know that Facebook wasn't involved. But I would believe that kids 5-7 would believe something like that.
I say it all the time. My generation is the last one that will have any ounce of common sense. The internet has changed everything.