I listened to Firpo's comments. He's repeated the story at least twice. He carefully sets it up as a private conversation between him and Michael. He gives a lot of believable detail, but the actual story doesn't ring true. Why would Michael Jackson be concerned about his children studying the Bible with Jehovah's Witnesses at some time in the indeterminate future when they could have done so anytime. I got the impression that the nanny was a JW also, so a "study" would have been easy to arrange if desired.
tms