One of the newer bloggers at Freethought Blogs tries to claim there isn't.
In the sense of a "creed," true, there might not be
such a thing as atheists fundamentalists. But, in the sense of atheist
evangelistic fervor, including willingness to misread/misinterpret
polling data and other things, ohhhh, yes there is!
And, from P.Z. Myers on the sexuality of Gnu Atheists on to Penn Jillette, Al Stefanelli (who posted the linked story on Google Plus), Center for Inquiry and MANY others either ignorantly or else deliberately confounding/confusing "irreligious" with "atheist" on sociological polls, Gnus do exactly this An.
The specific column does its share of twisting in other ways.
1. Theistic evolution doesn't "deny" evolution. I personally think a deity is superfluous to the process, but, there's no way of PROVING that. And, if a proposed deity's interventions were generally on the rarer side, on the non-massive amount of change side, and especially if said deity weren't necessary omnipotent or omnibenevolent, wouldn't deny evolution at all.
2. It assumes that "fundamentalist Christianity" = "Christianity." Common, often deliberate, tactic of Gnus. Many liberal Christians (though perhaps still not often enough and forcefully enough) not only separate themselves from fundamentalists, but denounce their tactics and beliefs. And, no, Mr. Atheist Fundy, religious moderates and liberals do NOT accommodate them.
3. It assumes that "Western/Middle Eastern monotheism" = "religion." Given that Hindus plus Buddhists in the U.S. likely now outnumber Muslims and perhaps Jews, and given that, worldwide, Hindus plus Buddhists are approximately equal to Christians, this is a huge error. And, then, you have a Sam Harris multiplying the cheating by trying to claim Buddhism is "just a psychology."
4. Like other Gnus, this one in particular is a fundamentalist, psychologically, for another reason - he's not open to discussion and argumentation beyond the straw person level.
And, that's why I don't engage Gnus too much myself. It's also why "atheist" is far and away from being my only philosophical self-descriptor, and why I can see "apatheist" has attractions for many.
That said, one commenter on the blog does correctly note Gnu Atheism as an "identity movement." Anyone who knows the sociology of identity movements knows that they often wind up headed to Trotskyist purity drives, a secular fundamentalism indeed. Trotskyist socialism itself as well as Randian economics are two clear examples from the 20th century, and yes, both are "fundamentalist" movements.