That and the Shouting Fire thing are both directly harmful. Calling yourself an engineer, not a PE, without a a PE is not directly harmful, and the Constitution overrides state laws that claim otherwise. My money is on him in this one.
"Shouting fire" is a reference to Schenck v. US which has been overturned. It applied the "clear and present danger" standard. The current standard is "incitement to imminent lawless action" as articulated in Brandenburg v. Ohio.
There are more limitations but that's an easy and possibly counterintuitive example.