And let's not forget the all-time classic about "satanic" rock albums that took too long to burn when you tried to set them on fire.
When I was still in, I made a point of debunking that one, too... "They're made of vinyl, folks... it's a specifically slow-burning material. Even the Society's records would take that long." I'm sure you can all imagine how well that info went over (you know, in retrospect, I think I was as much of a shit-disturber then as I am now ).
With those stories - and the "backmasking" thing - you can imagine my relief when CDs became widespread... they melted easily, and you couldn't play 'em backwards even if you wanted to, so the superstition old-timers would finally have to shut up about it.