I'm not sure which "nutcases" you mean. Here are some of the "nutcases" quoted in the essay and on his Web site and blog:
"Fringe groups"...like the Sierra Club, the Wilderness Society, the Nature Conservancy, the Natural Resources Defense Council, Greenpeace, the Humane Society, the EPA, etc.
"Nutcase positions"...like those of Al Gore, John Muir, Paul Ehrlich, former New York Times environmental reporter Philip Shabecoff, New York Times reporter Nicholas Kristof, Henry David Thoreau, Rachel Carson, biologist George Perkins Marsh, U. S. Forest Service founder Gifford Pinchot, Aldo Leopold, Bill Moyers, Carl Sagan, Humane Society vice-president Michael Fox, Humane Society executive director John Hoyt, the text of the Wilderness Act of 1964, etc.
This doesn't seem to be the "extremists" and "nutcases" he's quoting, but the "mainstream" environmentalists. I think the point of the essay is that the "mainstream" environmentalists and the "extremists" believe a lot of the same crazy things. If that's the case, then the argument that he's picking on only "straw men" seems to collapse. Or am I missing something?