I’d agree with you where Denton is concerned. But there are certainly cases where it IS fine. An example I gave to Shedinger (which was then deleted, whether at his urging or not I do not know, from the blog) was that if I recommended a book criticizing Christian belief to you, and upon opening it you found that the principal argument in it was that Jesus could not possibly have parted the Red Sea, you would immediately realize that a person whose misconceptions of what the Bible said were this severe could not possibly be the author of a worthwhile critique.
Such examples abound. There are paragraphs from Eberlin’s book, for example, one of which I cite in my Amazon review, which alone demonstrate that the author’s competence in biology renders anything he may say quite useless. There is the statement in Shedinger’s book:
“Those who argue that a Darwinian microevolutionary process can account for the origin of higher taxa base their view on imagined scenarios, not documented evidence, such as when we are told that the bones of the reptilian jaw evolved into the bones of the mammalian inner ear.”
That’s it; game, set, match for the possibility that the man has written anything that anyone must take seriously.
Now, to be clear, I do not think anyone should write a book review on the basis of such a conclusion. He should find a table leg that needs propping, and put the book to use. But it is quite right to dismiss an author on the basis of 1% of his work, if that 1% is bad enough. The list of ID authors of whom this is not true is quite short. I insist on reading them anyhow, but I cannot be sure it enriches my life much.