I am rather new to the community, but I would like to weigh in on this subject. I think IRL most people are good at heart and this makes playing a "slaver" hard as, over time like some have said, real life morality worms its way into your characters. I think the biggest thing that people (Amarrians in this case) do wrong is how they think of slavery.
Most people in the Eve community focus on Colonial Era United States or 1980's South Africa when they think of slavery (yes I know South Africa wasnt a slave country 1980's but go with me here). They think of whips and chains, murder, rape and all the other sorts of vile things that go along with he modern thoughts on slavery, this however is not a good reflection of Amarrian Slavery.
The Amarr Empire is a religious empire, ordained by God, to bring his(her?) love, teaching and word to all beings of New Eden. The downside is that only those who were born Amarr are capable of receiving God by "Grace" (ie by the simple acknowledgement that God is God, the saviour of man and all that). Those not born of Amarr cannot receive the word of God by Grace, but by works (ie they must earn God's love). There are many forms of "works" and it isnt always a slavery process (see Khanid and Ammatar).
When a Holder gains that religious title, it means that they (in theory) are of such virtue and piety that they have been deemed trustworthy enough to guide the lost souls of New Eden to the word of God. Look at "The Burning Life" where the agent character goes to the Amarr to find solice. It is described as a day filled with religious reflection, working of fields, sermons and more religious reflection. She took on "works" of her own accord and thus is not subject to whips and chains, whats more as some one who came to God, instead of God's servants having to come to her she is afforded the right to leave when she wishes, the thinking being "she has come to God once of her own, she will return".
Those who do not come to God on their own (Minmatar) must be made to be redeemed, still through "works". This is more akin to a parent saying to a child "this hurts me more then it hurts you" as I think a properly RP'd Holder is more concerned with the redemption of a mans soul then the economic boon of not having to pay for labor. Not much has ever been said of what an Amarr slave plantation looks like but I would assume that it looks like early morning prayer, meal, working, prayer, lunch, work, sermon, dinner, shower, religious reflection, sleep. Beatings on plantations would be more akin to "torture the flesh to save the soul" mentality then "im just a cruel and sadistic bastard muwahahahahahaha!"
I think if you look at slave holding in this light, it makes it more palatable to play while keeping your character more human to your real life sensibilities. Now dont get me wrong, I am not going to go all Eran Mentar and stop RP'ing a Minmatar that hates you for what you do, im just trying to help with some RP ideas for those who may be thinking of this line of play but find common thoughts on slavery to hard to foloow through on.