Because a lot of Slashdotters are libertarians who only have the most cursory understanding of social philosophy, the Constitution, what lead to it, who created it and why, and are about as sensible as the Communists of the last century.
Rights exist because a majority of the power structure in a society agree that they do. Where that agreement comes from is rather irrelevant - church, open fora, private discussions, backroom deals between cigar-chomping fat cats, a sentimental upwelling; it all works the same way: at some point, enough people agree that some rights are useful or fit into the current moral philosophy, and decide to enforce them.
That's why equal rights for gays are being accepted now, that's why Freedom of Speech is central to how the US operates politically, and why gun rights in the US are sacrosanct.
Babbling on about natural rights is as useful about babbling on about what Nature "wants".