>Where this loses me is: 1) I don't think "it's inconvenient" (that is, it empowers tyranny) is a compelling argument for or against the truth of something

Oh, ok. But what about the part where it exists without society? In the US, for example, our laws are mostly reactionary. It's built on the common law system, and things change over time as they encounter new situations. So rather than creating a law to create the new, the law is created in response to the new.

>2) I don't see how this, in fact, affects the practice or existence of tyranny one way or the other.

Do you not see that in practice or in theory? Because in practice sure, it's hard - the concept of rights stemming from the individual is mostly an enlightenment one and that's only a few hundred years. That said, countries that follow that principle have not had a tyrant lead them for more than a few years over that period either, while countries where rights come from the state have had tyrants or monarchs. That doesn't really prove anything but if you go into the theory, one system supports centralized power and the other supports decentralized power. Which is better for consolidation and control by a smaller group?

>The reason I think it matters is because I think it's harmful when people get really hung up on some set of rights that they believe are proven from a hypothetical argument (as the "state of nature" argument is—often this ends up being heavily centered around individual property rights, as in Locke) and draw a hard line between those and any other liberties that others might like to admit to the ranks of "rights".

Could you make an example? I'd be surprised that someone can be for natural rights and be against say the existence of a right to free expression, for instance.

>You can contest whatever you want, if you're able.

Sure, my point is that it makes you more able. People want to be on the side of justice and morality and it's important to have deep foundations for individual rights to assist in preventing the government from succeeding in its attempts to usurp them. Governments always try to usurp people's rights, but it's harder to do when individuals know it's happening. I think it's better to be suspicious of the government when it increases its own power. If you believe your rights come from your government then when the government limits your potential actions you are less likely to object - you'd sound ridiculous. I believe it's these minor objections that lead to larger movements and allow for change without direct and bloody revolution.

This part, for example: If someone's contesting slavery and you convince them that the "natural rights" conception is bunk, they can... still contest slavery. It doesn't matter a bit.

That's true but if that happens it stays a single person contesting slavery with no real basis in ethics. Why do they want to deprive people of their property in contravention of existing rights and laws? Why not have slavery outright, actually, in that case? What's wrong with it? Is it only wrong because the state currently says so? I don't think so - I think it's wrong for a lot of reasons but at its core, a person owns themselves, always. As a result they cannot be fully owned by another.