Under atheism, there really is no right and no wrong; to assert good and evil is to, in my opinion, betray a closet theism.
Actually, I'm establishing that I don't want to be a slave. I haven't said anything about a why. By establishing that I and all others don't want to be slaves, I've established a wrong by virtue of universality. That some might like to be enslavers is immaterial.
Take an example of photography. Some would like to be photographed, some wouldn't want that at all. Some would want to be the photographer, others not. Some neither, some no preference. There is no universality and no morality or wrongness with respect to photography.
I'll put it another way. In a given activity there are roles to be played: murderer, victim; photographer, model. There are hats associated with each role and everyone gets to put their name into as many hats as they are willing to play the role associated with it. Where you have hats with no names, there's something moral and wrong going on with that activity. Where you have hats containing every name, there's some moral and right going on there.
If you are the slavemaster, slavery is quite a wonderful thing. Better than home automation. You may end up reasoning to yourself that it's the "natural order of things" that you rule and the slaves are ruled by you.
There may be any number of people who argue this. If they argue it is right for them to own slaves, but that it would be wrong for another to own them, they are being hypocritical.
to assert good and evil is to, in my opinion, betray a closet theism.
Would that I were. You theists have a much easier row to hoe.