For some, that belief system could be called Darwinism. Yes, I know, evolutionary theory has passed beyond Darwin. But Christianity, likewise is practiced, in its various forms, as per the teachings and modifications of St. Augustus, Martin Luther, Joseph Smith, etc. etc. etc., while still being Christianity. Other atheists choose other guiding principals than Darwin. Other theists choose other religions that Christianity. For that matter, some people work with a mishmash of sometimes conflicting beliefs.
So atheism is not a religion, per se, any more than theism is. Both are classes of belief systems. However there are certain atheistic beliefs that fill the role that others fill with theistic beliefs that are classed as religions. These atheistic belief systems that fulfill the roles of religion -- Dare I call them atheistic religions? Is there another term that could be used? -- are as potentially subject to closed-mindedness, doctrinairism, fundamentalism, and being used as an excuse for tyranny, as theistic religions.
Is is possible to believe in evolution without it taking on the role of a religion. Heck, I believe evolution at least played a major role in the development of life on Earth. But is also possible for a scientific belief in evolution to become the atheistic religion of Darwinism. And for some Darwinists to become fundamentalists, in the manner that Richard Dawkins has.
In that, I consider Johnson's article to be on-target.
Belief and faith are a way of viewing reality. The alternative to belief is skepticism, not other beliefs.
The two camps often overlap, and there are supporters of each who are quite fair-minded and reasonable as well as some others are considerably less so. I also agree that Christian Fundamentalists deserve credit for being open about their fundamentalism, and I would give that same respect to a Daniel Dennett, who is equally open about his. Those who would dispute that there are fundamentalists in science as well as religion should take note of Dennett's words about himself and his close friend and associate, Richard Dawkins:
And I also thought, on rereading the book, that the late Steve Gould was really right when he called Richard and me Darwinian fundamentalists. And I want to say what a Darwinian fundamentalist is. A Darwinian fundamentalist is one who recognizes that either you shun Darwinian evolution altogether, or you turn the traditional universe upside down and you accept that mind, meaning, and purpose are not the cause but the fairly recent effects of the mechanistic mill of Darwinian algorithms. It is the unexceptioned view that mind, meaning, and purpose are not the original driving engines, but recent effects that marks, I think, the true Darwinian fundamentalist.
And Dawkins insists, and I agree wholeheartedly, that there aren't any good compromise positions. Many have tried to find a compromise position, which salvages something of the traditional right-side-up view, where meaning and purpose rain down from on high. It cannot be done. And the recognition that it cannot be done is I would say, the mark of sane Darwinian fundamentalism.