I have non-religious Iranian friends, living in Iran, that will share their views with others and certainly do not live in fear of their lives. It is a complex topic however. Much of what a western person might associate with 'religion' is better attributed to 'culture'. Openly rejecting all cultural norms, unlikely to go well, foreigner or local, Iran or elsewhere. Your comment does not provide meaningful understanding and rather misleads.
I have met people from middle eastern countries who are apostates, a crime punishable by death. They fear for their life and the history of executions in countries like Iran and Saudi Arabia, to name two of several, is clear.
It is undeniably true that in Iran and several other countries, blasphemy and apostasy is a crime. A real, actual thought crime which the state punishes with violence.
So it's the state you are concerned about? Not common Iranians?
>> Wanting to go study the beautiful works of art in Iran is brave. As an atheist, it would be dangerous for me to do so... But yet, it's still true that many, perhaps most of them [Iranians] "hate my kind" over there.
In practical terms, for your trip to Iran, US citizenship is a more likely source of potential issues than your religious beliefs.
Yes, I am more concerned about authoritarian states than individuals generally.
And yes, my passport would pose a bigger problem for me on first blush. But even for a European in Iran. Or an Iranian in Iran, apostasy is a crime and one that can be severely punished. We should decry that as a threat to freedom of thought and religion.