Just some questions, that you could take as rhetorical questions.
Do you think slavery is the normal natural state because people ought to be slaves naturally?
How about those who don't want to be slaves, are they going against the laws of nature, according to you because people are meant to be slaves of a group of masters?
And because you and other people say it's biology, do you think I or others (voluntayists) should just accept our slavery because you and other people say so?
Do you see that it is not possible to convince an voluntayist ;) that he or she should just accept his or her slavery?

Peace

Edit

In how far should we take this voluntarist approach and way of thinking?

That is totally up to you in how far you take that approach. It's your choice and I guess choice, in a way, is what differentiates us, in at least one way, from animals.