Not to put to finer a point on it, but of course being an atheist makes you stupid. It can’t not make you stupid if you try to take it seriously and not just half ass it the way the new atheist clowns do. Atheism implies a certain metaphysics about the world, this is unavoidable as the atheist cannot consistently hold to a metaphysics that logically concludes their is a creator.
As a result, with the thin and sub-standard metaphysics they are forced to embrace, they are forced to constantly deny things about that cannot fit and cannot exist.
The usual one they start denying is morality but when followed consistently, you need to deny, knowledge, mind, consciousness, reason, logic and ultimately even the idea of composite objects. Why they choose this part to nihilistic madness rather than embrace a generic theism (Deism cannot provide the metaphysical foundation either) is beyond me, but they do.