Not content to undermine a NATO ally and wipe hundreds of billions of dollars in value from global stock and currency markets, President Trump followed up last week by punching a revered American company in the gut. The motorcycle manufacturer Harley-Davidson, celebrating its 115th year in business, offended the president by having the temerity to move jobs to Europe. The company did so because tariffs that Mr. Trump imposed on imported steel and aluminum, combined with countervailing tariffs from the European Union, raised Harley’s export costs by some $2,200 per bike. Unable to pass that on to European consumers, Harley acted in the face of mounting losses. “Many @harleydavidson owners plan to boycott the company if manufacturing moves overseas,” Mr. Trump tweeted. “Great!”

No, it’s not.

The stage for Mr. Trump’s corporate mugging was his country club in Bedminster, N.J., where he likes to cheat at golf on the weekends. There, in what used to be horse country, rode in a group of so-called Bikers for Trump. The old white biker dudes were invited by Mr. Trump because it’s likely that none of the old white golfer dudes at his club ride hogs; they’re more Audi than Harley.

These motorcyclist agitprops are emblematic of Harley’s current problems, and why Mr. Trump’s misguided trade strategy is hurting the company’s employees, its shareholders and our economy. More American companies and workers will suffer if his trade war continues, even though, you know, we’re “winning.”

In the United States, Harley has been trying to get younger. (Aren’t we all?) As aging boomers like me who form the core of the Harley cult ride off into the sunset — some on their motor trikes — Harley has been recruiting a younger and more diverse group of riders to replace them. This is a smart strategy, but the company has had mixed success so far. HOG, as Wall Street calls Harley, has in fact attracted younger riders, including women, but not quickly enough to replace the departing demographic and to expand sales. For boomers, a Harley was a two-wheeled middle finger, whether you were an outlaw Hells Angel or reported dutifully for work at a Fortune 500 company on Monday morning. Millennials’ digits are on their smartphones — they aren’t that interested in driving at all, never mind a motorcycle. Unit shipments of Harleys will decline 4 percent this year, according to Morningstar .