QUOTE FROM THE RULING:
MR. JUSTICE BLACKMUN, joined by THE CHIEF JUSTICE, MR. JUSTICE WHITE, and MR. JUSTICE REHNQUIST, concluded that car card space on a city transit system is not a First Amendment forum, and that here the decision to limit transit advertisements to innocuous and less controversial commercial and service-oriented advertising -- thus minimizing chances of abuse, appearances of political favoritism, and the risk of imposing upon a captive audience -- is within the city's discretion, and involves no First or Fourteenth Amendment violation. Pp. 302-304.
Lehman v. City of Shaker Heights
Nor was there a captive audience whatsoever. DMV business was in the building. He was well away on the sidewalk. He was NOT using a bullhorn. No one was "captive." If he had gone in the building doing so there claiming it a public facility, they might have a point.