There is the possibility of psychological reactance, though, or something similar. Maybe some atheists feel so heavily pressured by theistic explanations of conscience that they shut down and refuse to explore those explanations even just in the abstract. Maybe they feel so much aggressiveness or hostility toward theism and/or theists in general that any exploration of theistic concepts is bound to remain superficial and imprecise. Maybe ... It's strange though, given that the thread was intended as a mere exercise, strictly assuming that God does not exist. Nevertheless, for the sake of argument, can you think of some? All the refutations I can think of work only with an inferior definition of "god" (ie. a demigod), and there have been plenty of those in this thread already.