Note too that inalienable does not mean irrevocable. The state will not enforce a contract of slavery, for example, (i.e. the right to liberty is inalienable), but it can, of course, revoke your right to liberty by putting you in prison and forcing you to work.
Also note that legal rights and rights-as-social-constructs certainly do exist, and have a profound social and cultural impact. Saying they do not exist "objectively" is not really relevant. Yes, we could choose to not construct, for example, a right to liberty, and it has been actually true in the past that societies have existed for many centuries without constructing any such right, but the fact remains that in most Western nations, we do in fact choose to construct (albeit imperfectly) a right to liberty.
Also note that legal rights and rights-as-social-constructs certainly do exist, and have a profound social and cultural impact. Saying they do not exist "objectively" is not really relevant. Yes, we could choose to not construct, for example, a right to liberty, and it has been actually true in the past that societies have existed for many centuries without constructing any such right, but the fact remains that in most Western nations, we do in fact choose to construct (albeit imperfectly) a right to liberty.