I have to admit, I wouldn't bother to think all that much about (in character) killing a bunch of orcs to free their slaves. I certainly wouldn't put as much thought into it or try half the things people seem to expect SemperJase to do. Granted, they expect this of him because of his stand on morality in gaming (and this is not a stand I share) but still, if while gaming you see a pack of orcs holding a group of captives, it's generally accepted that the heroic thing to do is to attempt to liberate them.
The Civil War's a hard topic because people to this day have strong feelings about it. To my eyes, the South committed treason. The states that seceded did so without any mechanism in the Constitution for it, and then siezed US Government property by force and took up arms against it. I know a lot of people don't share this opinion (I've lived in the South) but as far as I can see, slavery is and has always been an evil practice and all the societies that practiced it knew that, or at least individuals did...from Hesiod and Xenophon in ancient Greece to Tacitus in Rome, there were always those who decried the practice, and no one wanted to be a slave. (I'm sure you could find one or two people who, raised as slaves, did not want to be freed...but such is explainable by acclimation, much as people today who are more comfortable in prison than free. This does not make imprisonment desireable, and that practice at least has as an intention the ideal of addressing wrongs and injustices. Slavery does not.) Slavery is as close as any human practice outside of genocide to an absolute evil. (For that matter, many human societies have practiced genocide in human history, and that doesn't make genocide any less wrong.)
I don't think playing an evil character will warp anyone's mind. I've done it. I've played a character who deliberately and with malice aforethought overthrew the rightful government of a world-spanning empire and then used that empire to try and destroy the world. (Yes, I was the DM at the time...but I played Sejuk Mejur to the hilt, as far as I could take him.) I've played a character who was 'lawful evil' and who made it his life's mission to hunt down and kill every descendant of the woman who exiled my family. The fact that his ancestors were in fact guilty of the crimes they were exiled for didn't enter into his duty, playing that character. And as each session ended, I was capable of leaving the game and being myself again.
I don't agree with SemperJase's stand about evil characters, not at all. But I don't think trying to twist his party's actions in this case until they are evil actions in order to show him the error of his ways is fruitful here. For one thing, this *is* a game, with certain genre conventions. Secondly, the moral and ethical codes of a party of adventurers in a fantasy setting are not our own...for one thing, they're a lot more liberal with the lethal force than I would be in real life. In history, which is not fantasy but which often informs it, men who were later considered Saints like Louis IX of France led armies into battle and killed their fellow men. Louis genuinely was one of the most charitable, pious, generous men ever to live (he founded leper hospitals at a time when most were unwilling to and visited them, he was a great lover of erudition and supported monasteries to increase the level of learning in his land), and yet he slaughtered Saracens for no other crime than being in the Holy Land. This at once shows how morality is relative and yet how absolute it can be at the same time, and it shows how hard it is to gauge motivations.
It can be interesting to bring such elements into a game, of course, and I'm not trying to stop anyone from doing that. Yet expecting every single encounter to be one of tightly measured moral judgements is kind of taking things too far for the game to remain enjoyable, to me anyway. Not that anyone's said that, but the distance this back and forth discussion as to the justifiable nature of killing the orc slavers has run tends to imply that, to my mind.
So what am I saying, exactly? Well, first off, I don't think anyone is going to convince anyone else to change their positions here, but we all knew that. Secondly, that while the subject of how much flexibility a game will have morally is a good one to discuss, it should remain second to the primary goal of playing the game. Thirdly, that in my own experience playing an evil character or characters either as the DM or as a player is no more morally or ethically corrosive than reading a book or seeing a film or writing or acting or even just sitting back and imagining. Furthermore, I would argue that *every single human being in the world* has a capacity for evil, and that blanket dismissing the possibility that exploring such a capacity in the relatively safe confines of a game has merit is a bit rigid for my imagination. I've played Aashuran the Whisper of Death. At no time did I forget that I am not really him.