Many terms of art from economics are probably not widely-known here.
> In economics, a good is said to be rivalrous or a rival if its consumption by one consumer prevents simultaneous consumption by other consumers, or if consumption by one party reduces the ability of another party to consume it. - Wikipedia: Rivalry (economics)
Also: we should recognize that stating something as rivalrous or not is descriptive (what exists) not normative (what should be).
I'm either not understanding you or disagreeing. You seem to be saying that something should be because it is? Saying that would be rather silly, as in "Electrons should repel each other because they repel each other." Not to mention that this claim runs amok of the naturalistic fallacy. So what are you driving at?
But from there my point was that, in order to ask what "should be", you must ask what can be. I don't think there is a way for ideas to be non-rivalrous, period.
So sure, saying ideas are not rivalrous is descriptive, but there isn't really another option.
> In economics, a good is said to be rivalrous or a rival if its consumption by one consumer prevents simultaneous consumption by other consumers, or if consumption by one party reduces the ability of another party to consume it. - Wikipedia: Rivalry (economics)
Also: we should recognize that stating something as rivalrous or not is descriptive (what exists) not normative (what should be).