Being the 1930s I bet there was a lot of outsiders trying to capitalize on the demonstrations, and you can bet the Communists were, and that many, probably most, of those veterans were not the kind of men that we would admire.
A lot of our WWII vets were also lefties and socialists, both of those wars were manned by draftees, which highly diluted the general characteristics (politically speaking) of military men.
It seems as though the same thing happened during VietNam.