If humans don't own themselves, and there's no good reason as to why we can't just kill each other, then why are there laws against it in the first place?
Do you have the natural inclination to murder? A few pathological people do but the numbers are fairly low in wider society. For the rest of us sensible human beings, we don't need laws to tell us what's right and wrong. For how else could tribes exist? No written law existed yet they naturally took care of one another.
I want to quote the Tao Te Ching, an ancient text from 2500 years ago in China., verse 18 and 19:
18:
When the greatness of the Tao [consciousness] is present, action arises from oneÂ’s own heart.
When the greatness of the Tao is absent, action comes from the rules of “kindness and justice.”
If you need rules to be kind and just,
if you act virtuous, this is a sure sign that virtue is absent.
Thus we see the great hypocrisy.
When kinship falls into discord, piety and rites of devotion arise.
When the country falls into chaos,
official loyalists will appear; patriotism is born.
19:
Give up sainthood, renounce wisdom,
And it will be a hundred times better for everyone.
Give up kindness, renounce morality,
And men will rediscover filial piety and love.
Give up ingenuity, renounce profit,
And bandits and thieves will disappear.
These three are outward forms alone; they are not sufficient in themselves.
It is more important
To see the simplicity,
To realise one's true nature,
To cast off selfishness
And temper desire
The Tao simply means the subtle essence of the universe and is not important to understanding the point. Laws are external to human beings. Hell, has a law ever stopped you from doing something you are getting ready to do? For me it has only on occasion but it doesn't work all the time and so laws don't even serve the purpose you seem to think they do.
Morality is internal, it has a genetic component as well as cultural. We understand this through cross cultural sociology that examines behavior and identifies patterns that emerge. Shunning murder is among these patterns. So is empathetic behavior and consideration of other humans (which is conspicuously absent from the principles of anarcho-capitalism--"self interest is the only sensible way to go").
So I don't think you are asking a serious question. Instead you are trying to confuse the matter by raising issues that don't matter in the real world. Of course law is helpful but is by no means inherent and only serves as a mild deterrent, not a genuine prohibitive measure. Such measures can only come from within. We have major issues in the United States and the harshest punishments but we still have relatively highly "violent crime" rates compared to similar countries. So harsher laws does not address the issues of violence or murder. Either this is genetic or cultural to America. I firmly believe its cultural stemming from harsh living conditions and a lively gun culture.
Slave owners offered the same reasoning that we should have slaves because if we own something, we take care of them. This was a legitimate argument from the south in the 1850s. One can either romanticize slaves or you can look at how they were treated. If you approach the latter you realize owning people did not mean they were treated as they ought to be, namely, free beings.