He's arguing semantics in hope of misleading morans.
A corporation in that sense is any organized entity with a name. The United States is a corporation. General Electric is a corporation. The Red Sox are a corporation. And the He-Man Woman Haters Club is a corporation. These things can't not be corporations.
This mythology plays in the too-narrow common connotation of a corporation as a commercial enterprise. Neither the US or DC are commercial enterprises. But they are created entities with names.