That's why I never joined the VFW OR watched another Jane Fonda movie.
The war ended for many reasons, Nixon's resignation 8/8/74 chief among them as it gave political cover to ending the war; As well as a "heating up" of the Cold War in theaters that required more attention; lack of will not just on Americans but an exhaustion on the part of the Vietnamese for continued occupation by any foreign power. I agree the VVAW was a very public face that may have been one of the final straws that broke the camels back.
As to the OP, he is part of a long line of Vets. Grandfather was a Marine in both WWI and WWII, father served during Korea and Vietnam. And a cousin took his own life upon his return from Vietnam. 
The "spitting" issue, by whomever, is not a myth nor isolated incident, I'll leave it there.

Imagine if Mr Mussers history is anything like that, then he finds himself alone having lost even his house. And the final straw, they come to take his flippin trees! 
In his mind anyway....