Last week, I took note of something that antivaxers hadn't done in nine years, specifically a "march on Washington." Back in 2008, Jenny McCarthy and her then-boyfriend Jim Carrey led a rag tag rogues' gallery of antivaccine activists on a march and rally that they called "Green Our Vaccines." The name of the rally, of course, derived from a common trope beloved of antivaccine activists that I like to refer to as the "toxin gambit." It's basically a Food Babe-like fear of those "evil chemicals" writ large in a claim that vaccines are packed full of horrific chemicals that are Making Our…