Why Does the Objectivity of Religiously Grounded Human Rights Matter?

Fr. Araujo writes that "[t]he subjectivity that flaws the atheist’s conception of human rights is substituted with the objectivity that surrounds God’s existence."  My question is, how can that objectivity be demonstrated?  If it cannot be demonstrated, how and why does it matter to the cause of human rights?  It seems that religiously grounded conceptions of human rights are inescapably subjective and are based, at least in part, on believers' own experiences of the human condition and contrasting interpretations of divine revelation, as evidenced by evolving Christian convictions regarding slavery, religious liberty, women's rights, etc.  I agree that a belief in a God who seeks human relationship provides a firmer foundation than atheism for human dignity, but that foundation simply begins the conversation about the content of human rights.  In that regard, the atheist and believer do not seem that far apart.