When Securities and Exchange Commission (SEC) chairman Jay Clayton handed a policy win to corporate executives this month, he pointed to a surprising source of support: a mailbag full of encouragement from ordinary Americans.

To hear Clayton tell it, these folks are really focused on the intricacies of the corporate shareholder-voting process. "Some of the letters that struck me the most," he said at a commission meeting in Washington, "came from long-term Main Street investors, including an Army veteran and a Marine veteran, a police officer, a retired teacher, a public servant, a single mom, a couple of retirees who saved for retirement." Each bolstered Clayton's case for limiting the power of dissenting shareholders.

But a close look at the seven letters Clayton highlighted, and about two dozen others submitted to the SEC by supposedly regular people, shows they are the product of a misleading—and laughably clumsy—public relations campaign by corporate interests.