Within the context of the video game, I'm totally ok with enslaving whoever I like.
In reality though, by committing any kind of heinous or criminal act, you are acting as morally deficient/bankrupt as the person you're inflicting this act upon; which, in turn, makes you no better than they are.
As far as genuine crime and punishment goes, there's a reason why we have systems in place to prevent miscarriages of justice or acts of revenge, though, as we all know, nothing is perfect, especially when those who wield the power, misuse it, or it becomes a tool for others to abuse.
So, yeah, do what you like in a video game, but don't try to justify it unless you are genuinely insane, in which case you should probably take a moment of introspection to re-evaluate your decisions in life.