yabu, you should be discouraging them - two reasons, one is we never know for certain what we're messing with, second is that it's a load of bollocks.
Whichever - or both - you believe then you shouldn't be joining in.
I put two pencils on top of each other to demonstrate why it happens, without the paper or scary bollocks. It was that or some nice but stupid kid from our street freaking them out about it.