Well, now, you don't want that backwards-masked "Hail Satan" there.  In the case of those guys, I actually believe it was done intentionally.

I never understood the whole back masking phenomena.  Seriously, who first thought of listening to records backwards?  It was a good way to ruin the record, the needle, and the stylus. Furthermore, what were supposed to be crystal clear messages from the dark side were less than clear.  One could imagine them saying different things.  If you wanted to hear something diabolical, then that’s what you’d hear.  In many cases, one didn’t need to play the record backwards to hear bad music.  Just play the record as intended, forwards.  The songs praised evil without resorting to tricks!  
p.s. Viva, I did not watch the YouTubes because of the picture on the front.  Anything with an evil picture to get people to click on turns me off.