That is a brilliant observation by Ted Keer (which I didn't appreciate at the time).
But I disagree, to a degree, on one point. He said, "The concept of rights would never arise if there were not some (potentially objective) third party to which at least one of the parties of a dispute could appeal." That is true of the full use to which we put the concept of individual rights. But it is not the only use.
I'd say that what is being discussed here is the purpose of the concept. And purpose is a key context on its own.
One of the purposes of individual rights does involve the use of government (or the third party), but before that, and even if there were only two people on an island, the concept of individual rights would play a part. Individual rights are part of morality. Morality gives us what need to know in order to act, and we need a moral code even if alone on that deserted island. When a second person arrives, then we need the concept of individual rights to know what interactions are right. And without that, we would not be able to be rational and confident in our interactions with another. In a conflict, the person who is most certain of their moral standing (and rational in that understanding) is most likely to prevail.
But this is only a small quibble, on a small detail relating to the context of individual rights whereas that quote of Ted Keers is worth a great deal of thought. It is the kind of thing that can change how one approaches ideas as such.