The left-wing standard for doubting the veracity of the claims continues to be the inability to find corroborating news accounts at the time of the alleged spitting incidents, as if Vietnam vets were such whiny weenies that they ran like babies to the papers to complain "that hippie spit on me!" See the 1998 book by Jerry Lembcke which depends on this line of reasoning to argue the spitting incidents are a myth.
In our own time there has been a virtual news blackout on assaults against Trump supporters, especially during 2015 and 2016, which partisans point to as evidence those also are myths.
"If we don't report it, it's not news."
