Based on libertarian philosophy one is tempted to ask "who …

Based on libertarian philosophy one is tempted to ask "who has a better claim on your body than you do?" Which then makes the entire foundation of private property and by extension, ethics.
And to us today this seems pretty obvious and undeniable.
But any tyrant, king, slaver, communist robber, or rapist can simply reply "I do" or "WE do" and swing his sword or wield his power.
Self-ownership isn't as obvious as we would like to think. Without a metaphysical claim like "God set us free" or "God gave us rules that imply that everyone owns himself" there simply is no self-ownership, and therefore no private property or universal ethics, unless they are (temporarily and partly) granted or inforced by the rulers.
Nietzsche saw this very clearly and instead of just pretending that ethics are somehow obvious, like atheists usually do, he was consistent and proclaimed that there is no morality but moralities (plural). In particular slave morality and master morality.
Master morality doesn't at all accept the idea that the weak have ANY rights. On the contrary, they must be dominated or even exterminated for the greater good of a species on a trajectory of becoming better, healthier and stronger.
And he was right. In the absence of God morality must be determined by evolution. And evolution doesn't favor those who respect self-ownership. It favors the ruthless, the brutal and the selfish, like Genghis Khan, whose DNA is believed to be in around 16 million men today.
In religious terms you could call that the beast system. Humans who live their animal nature without interference from the soul.