Rationality doesn’t require atheism : ancient pagan societies had a place for rationality and didn’t subordinated material sciences to the religious like christianity and islam did. Contrarily to the received idea, based on a christian-like atheistic salvationist belief, obscurantism is an organized system, not the spontaneous dark nature of mankind.
Pagan scientists were not under constant threat of death by a theocratic terrorist obscurantist organization like they had been since the murder of Hypatia by christian monks.
The association of science with atheist beliefs is due to a christian history bias. For example, Empedocles had theories about atoms, matter, evolution and big bang, we call it philosophical myths, whereas today we call it scientific theories, proved, unproved or dismissed. Science has been described by some christian authors as the revival of pagan myths.
We have huge amounts of evidence that pagan belief systems had many myths and variants very similar to theories, and no trace of scientists condemned for not submitting and adapting their work to any pagan theologists.
Nowadays, in post-christian societies, science is far more hindered by unconscious religions in atheist minds than it ever has in ancient pagan societies.
Being pagan, or even identifying as an atheist pagan, allows to be used to make the difference between rationality and religious feelings. People born in atheist families are not used to discerning what is of religious nature when there is no explicit god or after-life paradise.
Being an atheist doesn’t make oneself a free spirit impermeable to overbeliefs, emotional bias, or representational prejudices.
There are many forms of predatory unconscious religions in the mind of modern atheists, since the decline of christianity and the establishment of liberal democracies, because religions had evolve into secular ideological forms in order to adapt them to the atheist public repelled from religion by the christian past : nazism, communism, monoracial faith, republicanism, and even good political faith like liberalism.
A follower of a secular or traditional religion is far more able to know his own credos and boundaries than an alleged atheist. Conscious atheism is not a pledge of rationality.