I wouldn't say those behaviours are foundational to atheism, atheism's foundations are pretty simple and not really enough alone to form any unified identity around.

Rather those behaviours being associated with atheism are the more the result of successful coopting and gatekeeping many years ago of the atheist-as-an-identity, such that other people who have no sincere religious beliefs and would technically be atheists shy away from the label because they want no part of that group's bullshit.

That's why agnostic became a thing, even though saying "I maybe believe in a god" is like saying you have no idea what's going on in your own head. People just wanted a way to say "I don't believe in God, but I'm not a pretentious cunt about it".

I wouldn't say those behaviours are foundational to atheism, atheism's foundations are pretty simple and not really enough alone to form any unified identity around.

Rather those behaviours being associated with atheism are the more the result of successful coopting and gatekeeping many years ago of the atheist-as-an-identity, such that other people who have no sincere religious beliefs and would technically be atheists shy away from the label because they want no part of that group's bullshit.