I feel I have good reason to doubt that you have anything beyond a vague idea of what fundamentalism entails. Coming from a place of relative ignorance, you seem to reason that fundamentalism necessarily must associate with religiosity, making your denial that such a thing as a fundamentalist atheist exists a tautology. You do this in the face of the fact that the "new atheists" have been popularly derided as atheist fundamentalists by their detractors since their arrival.
Fundamentalism, in general, can be correctly understood as an unwavering attachment to a set of principles, which may seem relatively harmless until you gain some insight into some of the psychology that goes into uncompromising "one way" worldviews such as wanting to create a worldwide caliphate or seeking the elimination of religious belief. Beings like you who give into such thinking then reason that they are what is right with the universe and those on the other side is what is wrong, and will proceed to angrily accuse the other side of their own very worst offenses. You love to point out Islamic genocides, yet you and Jihadists both hope for the elimination of everyone who doesn't think like you do.