Stoicism seems to be the default position for atheism (small “a”). That means that without thinking about it, the usual response from an atheist is a stoic response.
HOWEVER, there is nothing about Atheism (Captial “A”) that demands, requires, presupposes, etc. that Stoicism is the ACTUAL default position. That choice remains with the individual.
What I find interesting that that Scientific Realism (I had to look that one up!) also seems to be a common philosophical position for atheists. It seems like Stoicism and Scientific Realism aren’t incompatible.