answering telos
The morals are decided by what is logically consistent. If you decide murder is moral then you are saying that another person can exert his will upon (kill you) you but you can't exert your will upon him (not be killed) (assuming you want to live, if you don't, then it isn't murder, it's assisted suicide). So it's logically inconsistent, like saying 2=3, which we all know to be false simply my empirical facts.
The case for property rights is this: you own yourself (if you need logical proof on this go search it, I just assumed it as true). When you are born you aren't born into slavery. No one can take your arm, eat it, and you'll be ok with it. So by owning yourself you can do whatever you want to do with your time, as long as it isn't causing harm to anyone (you aren't murdering anyone, raping anyone, etc). So if you decide to spend 8 hours to get money and then you buy property with that money, no one should be able to steal any part of that property or the money you worked for, unless you consent to that (social contract doesn't involve consent).
A culture without personal property would be sustainable only insofar as it would be moral, ie the people would have to CONSENT to give their property away. So if I work for 8h and you work for 4h I would have to freely give my 2h of work to you (in the form of currency or food or whatever). But this, as you know, has too many ways to go wrong... that's why communism doesn't work.

So there, I just proved morality is objective despite cultural beliefs (which aren't logical - if you are going to use tribes to base your arguments remember that we used to burn witches, commit infanticide, etc. the only logical argument that can be sustained is that an immoral action (murder) can become moral once you have consent (murder -> euthanasia, rape -> sex, theft -> giving stuff, violence -> martial arts, etc...)