stating his personal opinion about sleepovers? Note that he doesn't even say that you shouldn't do it. Gene R Cook wrote it in a book one time?

Hardly a ringing endorsement for your stance on sleepovers. Sounds like some tremendous fear mongering to me.

In my experience counseling families, I can tell you that when parents put so many restrictions on their kids out of fear it tends to come back to bite them in the butt when those kids grow up and resent their parents. But hey to each their own.