Someone also once accused the "Mister Ed" theme song of having a hidden satanic message if played backward. So one must take such things with a grain of salt.
The real backward messages that I have found in songs were usually very clearly sung or spoken. I'm not sure about the "turn me on, dead man" one from "Revolution 9", though, because although John Lennon loved to screw around with stuff like that, it actually sounds more like "nurn me on, nedmun." ELO's "Fire On High" has a good one that says "The music is reversible, but time isn't...turn back..turn back...turn back.."
My favorite one is from a Girlschool song. First they start singing "We are Siamese, if you please" and then a voice says "Hey you, don't you know you're ruining your needle?"