Okay, I'll bite. It's out of my area of expertise, but it's important enough to warrant speedy attention, in my opinion.

This doesn't answer your question as such, but what is implied in your problem is the distinction between slavery and free or wage labour not always being as clear-cut as we might think. I can't speak for other slave societies, but this distinction was often not clear in colonial America. Apprentices, chattel slaves, and indentured servants were a part of everyday life and all owed (for lack of a better word) a master of some sort forced labour. Freely working for wages with the right to choose an employer, rather than under the authority of the state and master, did not at this point necessarily appear distinct from some of these forms of forced labour. What we understand today as working for wages wasn't a major part of the economy and didn't exist as a clear-cut concept separate from slavery. Independence meant owning property and self-employment (to use a anachronistic term) rather than working for an employer. Your 'good "slave owners"' only existed here in the sense that the distinction between freedom and slavery could be quite blurred in early America for a large number of indentured workers, household servants, apprentices, and journeymen. It's also worth noting at this point slavery is already racialised, with indentured servants generally being white and chattel slaves generally being black. If you want to read more, Edmund Morgan's American Slavery, American Freedom and David Davis's The Problem of Slavery would be recommended reading (and available in any university library). Christopher Tomlins's Freedom Bound is very comprehensive but very, very dense.

What's important here is not to think that in nineteenth-century America there were 'good "slave owners"' who treated African-Americans well on their plantations. (I saw this idea hiding behind the question and this is why I responded to it). Slaveowners did claim to be benevolent masters to their feminine, childlike (or so they claimed) slaves, and they probably believed it. Slavery, though, was universally brutal. If you read Davis or Morgan, you'll see how the growth of slavery required Americans to dehumanise their African-American slaves. At the mid-nineteenth slavery, I'm not convinced even slaveholders who saw themselves as good paternal masters could divorce chattel slavery from the whip and holding absolute authority over their slaves - which excludes the idea of a master considering slaves as people. This was an institution built on the lash, slave patrols, bans on teaching African-Americans to read, censorship of abolitionist material in the mail, pass laws, censorship of abolitionist petitions to Congress, bans on freeing slaves, paranoia at the threat of a Haiti-style slave revolt. Even if a master wanted to be a 'good master' in the way you might be envisioning, slavery was totalitarian off the plantation as well as totalitarian on the plantation. Southern society would have considered a 'good "slave owner"' that I think you're describing an ideological threat to the southern slave system, and would not have tolerated it.

tl/dr: In colonial America the distinction between freedom and slavery was distinct and opened the door for halfway houses between them. But in the nineteenth-century South, despite slaveholders believing themselves paternalistic and benevolent, slavery was a system that in its very nature excluded the idea of such a 'good master.' Nineteenth-century American slavery demanded slaves not be considered as people.

I had a class at university about slavery, but it was about whole world slavery and not only about US, so somebody with better specialization might answer you more precisly.

As a general rule, societes in the past have been much more stratificated. It have not been seen as something unusual. Our modern views of slavery are usually exagarated and not acute. Mostly in hollywood movies.

For example in ancient rome there have been times where slaves, mostly house-slaves, could have better standard of life than pauperized free citizen. Of course usual standard is that higher you are in society, better your life is. That doesn't mean that lowest groups have to bee tortured and beaten regulary etc.

I hope that nobody will get offended by this comparsion, it is purely for the sake of argument. Imagine you own dog or cow or sheep. Of course you use them for your benefit. Of course you put your needs before theirs. But that doesn't mean you beat those animals just because you can (and it is important to say that you can't, like you couldn't do anything you want to your slave in history). How many dog owners you know and how many of them are psychos? Well, there can be found some, but that is not standard of majority.

You have slave because of labour. They are working better under threat of violence and other consequences you can apply to them if they dissobey. It is much easier than actual use of violence.

Most notable thing to consider with slaves is rebelion potential. It was found hard way that mistreatement of own slaves can lead to really bad situations for you or your family (as slaveowner). Notable examples are slave rebelions of ancient rome, with third servile war of spartacus being most famous one (73-71BC), succesfull rebelion of slaves at haiti lead by Toussaint L'Ouverture in 1791-1804 or peasant revolts through europe. Examples from US might include Nat Turner (1831) and John Brown's raid (1859). Of course there is more rebelions, but because of inability of slaves to organize are usually only local and usually supressed by authorities pretty fast and pretty bloodily.

My favourite example are spartans. Killing the slave without reason is usally forbiden and most of the times in history is considered a crime (even when it still happens). Same was for spartans, but every year for a time they declared a formal war against their slaves (heilots) and any spartan was free to kill slaves without consequences. It was unusual thing of rebelion prevention.

Much easier way to prevent rebelions is to find ways to control slaves without violence. Being nice to your slaves (like not selling their children away even if you can by law) makes them sattisfied enough to just work and live and obey. For example in ancient rome slave could earn enough money to buy his freedom. That is more safe way to gain freedom for a slave than is to risk rebelion without acces to weapons and inability to organize. Of course most slave didn't earn that kind of money whole life, but mere possibility of buying own freedom helped with slave-control. Other good habbit in ancient rome was to set your most loyal slaves free in your testament. They knew that if they would be loyal they might get freedom, mostly from generous master.

So to sum it up, what you ask is if there are any slave owners that have been "good" to their slaves, answer should be most of them were. Within limits of course. But history remebers those crazy ones more (like Publius Vedius Pollio).

I hope somebody will be able to answer your question with more emphasis on US history.