On video games: I have played plenty of those games, especially RPGs; thus concerning our role to kill.
It becomes natural that someone gets hooked by seeing a protagonist died/killed throughout the story. You could be sad (Aerith case, perhaps), mourn the death, and so on — but why would we not be sad by killing antagonists? I mean, they’re humans (or if you prefer, characters) after all. So why?
On the matter of that, playing Shin Megami Tensei IV is a really different case. It’s a game for adults for its theme – morals – and its features. Upon battling against a character – and killed him/her – I stopped a while and thought, “Is it a right choice? Am I not taking a wrong path?” Well, the game made me think so by offering choices in battle; picking your ideals, considering moral choices, and so on. Choosing a path of life (or if you prefer, love – love of an ideal) never has been like this in RPG.
The awareness it brings… How do you feel to kill someone in RPG?
Nevertheless, you will never make a clean slate. There will be always someone hurt.
In the 
Forgeries 