Oh, an agnostic. That's different. I never claimed you guys were irrational or shallow. :-)
And, atheists obviously have purpose even if they don't know or can't articulate it. God-given rights apply to everybody.
I don't understand this conflation of "rights" with "purpose". Maybe you should clarify what exactly you mean by our "purpose" in life. Is it "purpose" as in an externally-imposed positive obligation, or is it "purpose" as in that which makes us want to go on living? Or something else?