This is an established web-site which does focus very much on evolution and is anti-creationist. It would probably be more accurate to say that they are anti-young-earth creationist.
I've found it at times to be a helpful site where it focuses on science and does not expand into editorializing.
I see part of it as an extension of the impact that Young Earth Creationism has had over the last 100 years and particularly following the rise of the modern flavor of Young Earth Creationism that arose under the influence of Seventh Day Adventism and Dr. Henry Morris (I'm not tying the two of them together directly.)
YEC has done a very effective job of framing the question in modern American Society in such a way that many outside of Christianity see Young Earth Creationism as equivelent with the Christian Faith. This explains in part why polling in the US in particular often gets a high percentage of support for Young Earth Creationism. A majority of those responding to the poll do not have a clear understanding of the issue and the supporting information. They see this answer however as equating to "Do you believe in God."
Sadly, this is a strong dynamic in driving people away from Christianity who might otherwise be open to considering it more open-mindedly. They have accepted the framing of the question by Young Earth Creationists to tie directly to the Bible as the only acceptable interpretation and so they equate accepting Christianity with intellectual suicide and consider it no further.
This is the primary reason I can get passionate in a debate with a YEC'r who is implying or sometimes plainly stating that their position is the only "Biblical" position that relies upon a "literal" interpretation of Scripture.
It is not.
Further, an OEC position does not accept science first and attempt to make the Scriptures fit it. OEC has been a majority position throughout Church History although it has modified and been affected by scientific developments. YEC has modified as well. The current militant, exclusionary viewpoint is not typical of the position throughout Church History. There almost seems to be a delight in being irrational and appealing to it as faith despite ample evidence both scientifically and scripturally to the contrary.
Probably more than you wanted to know.
Just realize that the site you reference contains a great deal of evidence for an old earth, yet many there equate the terms "creationism" and "young earth creationism" as being equal. It's not a militant atheist site per se, although that viewpoint is certainly represented.