Bill Gates, meet Ned Ludd. Ned, meet Bill.

Ludd was the 18th-century folk hero of anti-industrialists. As the possibly apocryphal story goes, in the 1770s he busted up a few stocking frames—knitting machines used to make socks and other clothing—to protest the labor-saving devices. Taking up his cause a few decades later, a band of self-described “Luddites” rebelled by smashing some of the machines that powered the Industrial Revolution.

Apparently this is the sort of behavior that would make Mr. Gates proud. Last month in an interview with the website Quartz, the Microsoft founder and richest man alive said it would be OK to tax job-killing robots. If a $50,000 worker was replaced by a robot, the government would lose income-tax revenue. Therefore, Mr. Gates suggested, the feds can make up their loss with “some type of robot tax.”

This is the dumbest idea since Messrs. Smoot and Hawley rampaged through the U.S. Capitol in 1930. It’s a shame, especially since Bill Gates is one of my heroes.

When I started working on Wall Street, I was taken into rooms with giant sheets of paper spread across huge tables. People milled about armed with rulers, pencils and X-Acto Knives, creating financial models and earnings estimates.

Spreadsheets, get it? This all disappeared quickly when VisiCalc, Lotus 1-2-3 and eventually Microsoft Excel automated the calculations. Some fine motor-skill workers and maybe a few math majors lost jobs, but hundreds of thousands more were hired to model the world. Should we have taxed software because it killed jobs? Put levies on spell checkers because copy editors are out of work?

Mr. Gates killed as many jobs as anyone: secretaries, typesetters, tax accountants—the list doesn’t end. It’s almost indiscriminate destruction. But he’s my hero because he made the world productive, rolling over mundane and often grueling jobs with automation. The American Dream is not sorting airline tickets, setting type or counting $20 bills. Better jobs emerged.

Mr. Gates may be worth $86 billion—who’s counting?—but the rest of the world made multiples of his fortune using his tools. Society as a whole is better off. In August 1981, when Microsoft’s operating system first began to ship, U.S. employment stood at 91 million jobs. The economy has since added 53 million jobs, outpacing the rate of population growth.

Even better, the Third World is rising out of poverty because of improved logistics from personal computers and servers. This has dramatically lowered the cost of basic food, energy and health care. None of this happens without productive tools—doing more with less.

What’s most disturbing is that the Luddites never totally went away. How many times have we been subject to proposals that would tax progress? ObamaCare’s regulations froze the medical industry. Its 2.3% medical-device tax was even worse, discouraging investment in one of the few innovative health-care sectors. Mileage standards on automobiles were a waste of resources contributing to the moronic Detroit bailout in 2009. Even a carbon tax is Ludd-like, raising the cost of energy to slow its consumption.

There is a murmuring movement out of Europe known as “degrowth.” If this sounds to you like a cabal of cave dwellers, you’re not that far off. Degrowth Week in Budapest last summer featured enchanting sessions like this one: “Popular competence building against the Technocracy.” Channeling Ludd, industrial insurgents and sustainability samurais want to keep things the way they are, like the eco-protesters at Standing Rock. The site degrowth.org is clear about the movement’s unproductive goals: Consume less and share more.

OK, but do you want to give up Google Maps, Snapchat and future innovations? Pry them out of my cold dead thumbs. Surely Mr. Gates knows that his charitable foundation’s efforts to eradicate malaria and other diseases require a lot of productive capital and hard work. I can’t picture him clamoring to tax robots that lower the cost of malaria drugs or mosquito nets. That kind of tax would kill off the next wave of disease-killing productivity.

I don’t think Mr. Gates wants to be the poster boy for the degrowth movement. He knows how hard progress is. After PCs, Microsoft missed the start of every subsequent technology trend: browsers, video streaming, search, smartphones and cloud computing. Today the company is playing catchup with neural computing, which drives image recognition and other robotic cognitive skills. This type of innovation, even if it destroys jobs near-term, needs to be nurtured and encouraged. Burden progress with taxes, and degrowth is what you’ll get.