I play video games with my 9 year old nephew. Mostly minecraft.
  Sometimes he gets a certain glee out of cornering and torturing
  me in the games.

  It's an outlet for repressed rage from other parts of his life
  so I let him do it up to a point.

  But when it goes past a certain point, or invades my own
  personal value system, then I point it out to him. I try to
  subtle.

  One time, he was being an evil character who was killing The
  Prisoners in Minecraft. He had set up AI characters in a fence
  over a lava pit. I had to pull the lever.

  These NPCs (Non player characters) look and act like real
  players; they even have names like, "Bob the Baker", or
  "Isabella the Child" hovering over their heads.

  I'd type in chat, "Well, Bob, you committed the crime and you
  must pay. I'm sorry I have to do this but I must".

  My nephew replies, "Oh, they're not criminals."

  That's when I knew I had to step in a little and do some
  conscience guiding.

  Just before I'd pull the lever, I'd say "I'm sorry Bob", or "I'm
  sorry Isabella".

  With a few minutes of that, and my nephew changes tactics and
  has me try to break the prisoners out cleverly by tricking him.

  Ah.. now that was better.

  And so, in just a few minutes, it went from the glee of killing
  anonymous people and watching them burn into "I'm roleplaying
  evil and you must stop me because the Real Me has a conscience,
  but the character I'm PLAYING is evil".

  I believe he instinctively has a conscience but is temporarily
  caught up in the madness of power. Outside of mental disorders,
  I believe this may typically be the case for many people.

  It's also possible that he _knows_ how I feel about anonymous
  torture and changed the rules to make *me* feel better, without
  referring to my nephews view of himself.

  Kids learn how to make their parents/uncles/teachers/etc happy
  by giving them what they want. So, in the end, there's no way of
  knowing truly whether it was a conscience-shift or he was
  placating me. But I'm ok without ultimate answers. I just found
  the situation awkward and was uncomfortable torturing people.