It's a plain fact that evolution, as a theory, has long faced an internal crisis, with various evolutionists at each other's throats, even as it has over the past decade come under a withering critique from the intelligent design theorists. Philip E. Johnson ("Darwin on Trial"), Michael J. Behe ("Darwin's Black Box"), David Berlinski (in his famous Commentary magazine article "The Deniable Darwin"), William Dembski ("The Design Inference") and a host of other authors have shown that the Neo-Darwinian synthesis that is the backbone of contemporary evolutionary theory is so weak that it depends on the huffiness unto hysteria of its advocates to fend off its critics.
One of the favorite evolutionist ploys is to routinely confuse people by not making a distinction between the fundamentalist Biblical literalism of "Creation Science" and the simple creationism implied by intelligent design theory, which infers from the complexity of life the reasonable premise that it is improbable (to the point of impossibility) that said complexity is the result of mere accident.
The irony of Erb's comment that "Evolution...cannot be denied" is that he's criticizing the Catholic Church for being slow to accept changes in scientific understanding, when virtually the entire edifice of evolutionary theory is imploding from the forces of its own internal contradictions. Yet materialists, those who believe that all that exists is the natural order and that there is nothing outside that order, cling to evolution as a dying faith, lashing out at those who dare to question it.
As Philip Johnson points out, evolution as a theory has become a number of things, some larger than others. The larger the claims, the less water they hold.
The only brief I ever held against evolution was that it seemed to me to be improbable. Then I gave my attention to the ID theorists and they made quite a case for just how improbable it really is. The irony is that evolution is the high church of materialistic naturalism, which is a philosophy, not a science. For people like Erb, it's a matter of belief.