Slavery. Is it ok?

It seems to be a losing argument to say that slavery can be acceptable. However, in Aristotle's time, it was commonplace. This is not to say that the ancient Greeks were barbarians because of this. While, for example, the oppression of slaves in the U.S. up to the last century was obviously unacceptable  Aristotle shows the conditions necessary for "just" slavery (an oxymoron in the eyes of many, particularly Plato [Polit. 258 E. 259]). At first I couldn't believe in a justification for slavery, knowing that all men are born equal, blah blah blah etc. but let me give you the quote and I'll leave it to you to decide.

The Quote:

They think that as men and animals beget men and animals, so from good men a good man springs. But this is what nature, though she may intend it cannot always accomplish. 

We see then that there is some foundation for this difference of opinion, and that all are not either slaves by nature or freemen by nature, and also that there is in some cases a marked distinction between the two classes, rendering it expedient and right for the one to be slaves and the others to be masters: the one practising obedience, the others exercising the authority and lordship which nature intended them to have. The abuse of this authority is injurious to both; for the interests of part and whole, of master, a living but separated part of his bodily frame. Hence, where the relation of master and slave between them is natural they are friends and have a common interest, but where it rests merely on law and force the reverse is true.

Aristotle goes on to say that this means that slavery is not a uniform relationship and that all aspects of it can vary between every example.

-Aristotle, Politics, 1255

What the quote says:

Basically what the quote is saying is that while nature has the best intentions of equality, sometimes it just doesn't work out like that. Some people are born slaves and some born masters. Having a master paired with a slave is natural where they have a common interest and are friends, according to Aristotle. 

My Infallible Opinion:

Slavery has a bad connotation and for good reason considering the many atrocities committed under it's name. For the most part I doubt that slaves in any number have this wonderful, friendly and cooperative relationship with their master. However, I will concede that under the conditions mentioned, slavery could be the best option. If so, maybe I should get out of blogging as a hobby and start a slave/master matchmaking service. There can't be any laws against that, right? On second thought people would probably just think it's kinky and it would turn into a hardcore dating site....not my scene, oh well.

EDIT: As Aristotle worded the "acceptable" conditions for slavery, I can't really object to it because it is in fact a mutual decision. I can't justify denying that humans should have an inate right to freedom and equality at birth. Yet as it has been quoted above, it is more like the slave is choosing to be the slave. That kind of defeats the point of the argument doesn't it? So I must conclude that slavery under the dictionary definition is not ok.