I detect an implicit false dilemma.
Rights indeed exist prior to, independent of, and outside the framework of "collective agreement". This is easily demonstrable by reductio ad absurdum: did the Jews lack a right to life because the Nazi state "collectively agreed" they should be exterminated? (Of course not.)
On the other hand, appeal to God is useless simply because the respect for rights is (or ought to be) broader than any faith, or even mode of faith. This is also easily demonstrable via a simple rhetorical observation: atheists should, and generally do, respect and value rights.