Arnold worked as a technical writer for Boeing from 1961 until he left in 1971 to found Northwoods Studio. In 1974 he began contributing to Western Conservation Journal, which exposed him to the suffering of logging and mining families caused by environmentalist lawsuits, and marked the beginning of his public opposition to environmentalism. Between 1978 and 1981, Arnold was a contributing editor of Logging Management Journal. His 1979 magazine series, "The Environmental Battle", analyzed the utilization / preservation conflict, and won the American Business Press 1980 Editorial Achievement Award.
In 1981, Arnold wrote the authorized biography of Interior Secretary James G. Watt. Between 1982 and 1990, he wrote a weekly column for the Bellevue (Washington) Journal-American. In 1987, he founded the Free Enterprise Press, and began writing a series of highly acclaimed books on the environmental movement. His "EcoTerror" was included in the "100 Best Nonfiction Books of the 20th Century" Random House / Modern Library Reader's List. 
Arnold also gained note as a historian with his discovery of the actual founder of the National Forests of the United States after a century of mystery shrouded the origin in conflicting claims. An almost forgotten politician named William S. Holman created the concept and the initial legislation, as revealed in documents Arnold discovered in the National Archives. He was honored to present a paper on "The Unknown Founder of the National Forests" at the centennial symposium of the Forest Service in 1991. 
Environmentalists have challenged Arnold’s “Wise Use Movement,” launched at a Reno, Nevada conference in 1988, as inappropriately co-opting the term from utilitarian conservationist and first Chief of the U.S. Forest Service, Gifford Pinchot, who held different views on man and nature than Arnold and his movement. Arnold readily admits the borrowing, but disputes arguments that it is improper, a controversy that continues unresolved.
He has been successful at mobilizing political allies by exposing the large sums of foundation money that funded environmental groups and using case histories of environmentalist excesses in influencing policymakers to adopt his ideas. Many consider the policies of President George W. Bush to be taken directly from Arnold's work. Playboy magazine's May 2004 issue featured a profile of Arnold in the Playboy Forum, by reporter Dean Kuypers. Titled, Guru of Wise Use, its headline read: The spiritual father of the bush administration's environmental policies says we shouldn't be timid about timber. 
Arnold has built a network of academic colleagues to help analyze large-scale social movements, and told the Boston Globe that environmentalism is "the third great wave of messianism to hit the planet, after Christianity and Marxism-Leninism." The Globe commented, "'Wise users' charge that the environmental crisis has been largely trumped up as an excuse to take control of the nation's natural resources." 
Arnold's conclusion that movements of social change, including environmentalism, are fundamentally a kind of war was examined and found valid by sociologist Luther P. Gerlach in the RAND research document, "Networks and Netwars." 
His website, The Left Tracking Library, has become a standard source Template:Citation needed for profiles of activists, foundations and organizations that is used by policymakers, media, industry, and researchers. 
- At the Eye of the Storm: James Watt and the Environmentalists, Regnery Gateway, 1981, 282pp.
- The Grand Prairie Years, Dodd, Mead and Company, 1987.
- Ecology Wars: Environmentalism as if People Mattered, Free Enterprise Press, 1987, 182pp. ISBN 0-939571-00-5
- Trashing the Economy: How Runaway Environmentalism is Wrecking America, co-authored with Alan Gottlieb, Free Enterprise Press, 1993, 670pp.
- Politically Correct Environment, co-authored with Alan Gottlieb, Merril Press, 1996, 178pp.
- Ecoterror: The Violent Agenda to Save Nature, Free Enterprise Press, 1997, 324pp.
- Undue Influence: Wealthy Foundations, Grant-Driven Green Groups, and Zealous Bureaucrats That Control Your Future, Free Enterprise Press, 1999, 344pp.
- Freezing in the Dark: Money, Power, Politics and The Vast Left Wing Conspiracy, Merril Press, 2007, 444pp.