Somehow, "I'm right, you're wrong, no room for discussion" seems to apply to both.
EDITED TO ADD: To clarify, it's more about atheists or agnostics who harshly criticize other atheists or agnostics who don't think like them and don't accept that there are differences among non-believers. Sometimes they sound like fundamentalists.
This is a great question and while I understand the quick"no" responses, I think you raise a great point. Atheists can mirror similar mindsets, emotional habits, and thinking patterns to those of religious fundamentalists. We share similar meat-computers after all. As a former religious person I am careful to grow in the way I process info, view others etc to be sure I didn't just swap one unhealthy way of thinking for another.
There’s a sense in which all theists and all atheists are fundamentalists, in that the god they do or don’t believe in is a fundamentalist god - a literal god. No one “believes in” or “disbelieves in” a metaphorical god. Metaphorical gods are just figures of speech, and I’ve yet to hear an argument over whether figures of speech exist.
But more to your point, yes, fundamentalism is fundamentalism, no matter where you find it.
It is not so much that some atheists are adamant about their religious opinions as that they have associated beliefs about the nature of reality that they guard with religious zeal, and often they aren’t even aware of their beliefs.
It is the physicalist/reductionist philosophy, steeped in scientism. NO one truly understands this reality in which we find ourselves, and to cling to that failed philosophy is no different than clinging to some religious dogma.
The bottomline is this, theists believe in things that don't exist.
Atheists don't believe in delusions, and all gods are delusions.
I admit that I can be rather adamant about that.
Then again, I'm not advocating that people who don't (dis)believe be killed.
Btw, I'm also an anti-theist, and I absolutely do believe that all religion is evil.
So, there's that.
Wtf? Atheists can't be fundamentalists. There is no atheist bible. There are no atheist tenents or commandments. Atheism is simply lack of belief in a deity. Are there assholes and insufferable douchebags that call themselves atheists? Yes there are. But, there is no inner circle and no fundamentalists.
the major difference is that there is no such thing as a fundamentalist atheist. that's a silly concept. and there are stubborn people all over, no matter what category you choose, be it religion/lack thereof or carrots vs. potatoes. but fundie theists work hard not for their own rights, or the rights of others, but AGAINST the rights of others, and i don't see that as a defining characteristic of atheists, no matter how stubborn.