Rocket man

A guy towed a 25-foot rocket labeled “Viva Viagra” through Manhattan last month, and got sued by Pfizer for doing it. He argues that he didn’t mean to cause confusion, he’s just a satisfied customer, but the fact that he was doing it to promote his ad agency—whose business plan is unclear, and whose website incorporates other people’s trademarks as if they were advertising with the agency—may give him trouble because it makes him into a commercial user. Query: what would be the best defense for a pure, noncommercial Pfizer fan who did the same thing?