a)The idea of "alienable" rights is contingent upon the accepted definition of "freeman" in Western society. "Rights", inalienable or not, were not extended towards women, slaves, and the landless.
b)The Western legal code is largely the product of the works of that famous Athenian duo: Plato and Aristotle. Their works were heavily sampled by their Roman counterparts and the Christian philosophers that followed (e.g. Boethius, St. Anslem, and St. Aquinas). The begins of Western "law" is merely an arbitrary fusion of Plato's ethics with Christian scholasticism.
c)Modern Western saw its introduction in that tragic age historians call "the Enlightenment." Taking the hint from Machiavelli's works in the Renaissance, enlightenment writers expanded the Western legal code to become more liberal. Your "inalienable rights", for the first time in Europe, were now truly "inalienable" because they did not originate from Providence. Rousseau, Voltaire, Molière, Pope, Locke, Hobbes, and the very underrated, Montesquieu laid the foundation for the Western legal system. They combined Plato's ethics with the spirit of utilitarianism which was in the air and tragically created the idea that "Law" was the fundamental pillar of rationality and a defining feature of civilized societies.
d) It is all a sham because it is all built on the view that there is something intrinsically valuable in each and every human being, except that the definition of "human being" was still largely up to the elite. Pre-Darwinian biologists long argued that Blacks weren't the same species as the white, western Europeans.
e)"Due Process" and "presumption of innocence" and etc. was created by the baronies of England to protect their assets against the whims of a monarch. It was only much later that those "rights" were extended towards the plebeians.
All of the above points, a-f, have not kept pace with the more important philosophical developments. Non-philosophical academic and legal institutions of the West have longed used Kantian philosophy to justify the supremacy of the Western legal code, but often forgetting that Kantian philosophy blasted some big holes in the idea that human reason reigns unchallenged over all other imperatives. Philosophers following Kant's discovery,most notably Schopenhauer and Nietzsche, have vociferously argued that the entire of Western society is built is nothing but a series of successive flaws. In short, it's all a sham.
But take heart, Erasmus praised Folly and reminded us all that we owe our very existence to the mistakes our fathers have made. Nietzsche reminded us that folly is a necessary condition for human survival. So, what does it matter that the entire Western legal code is a shame, right? All that matters is that it works for the majority of us.