I've got to agree that showing one card is an unfriendly move at the card table. You're entitled to do it, but it's an angle. Please understand that I'm not attacking anybody, but I don't find the argument that players like knowing they folded correctly is persuasive. The fact that they folded indicates there is a chance they are aware enough to be offended by this tactic.

As far as turning over legally mucked cards, if your arm/hand doesn't end up broken it's your lucky day. Go play some roulette.