“So in that case, if everything is relative,”
What do you mean by “relative”?
“if anybody wanted to steal from you, it ought to be permitted and not prevented, right?”
No, it ought to be permitted, you also ought to give me money while you’re preventing others from stealing from me. You ought to make payments using bills of twenty or higher. If you’re going to make payments digitally you ought to make payments divisible by five.
“Or does force determine who lives?”
It’s in the nature of our very universe that physical conditions always determine who lives and who dies. If one individual has extensive enough a control over the physical conditions in which another man lives then he will always determine whether or not the other man lives. Morality and rights ultimately have nothing to do with it.
“For instance, you could use your relative stance that theft is wrong (presumably, of course) and physically prevent the thief from stealing.”
Of course I can, is this impossible if morality is objective?
“Is liberty relative too?”
It depends on what you mean by relative.