Oh BS. My father was a Vietnam era vet (served in the Atlantic fleet) and he was welcomed by the VFW with open arms. And my memory of going to the VFW is that Vietnam vets were always around in large numbers at the functions.
Now, scumbags like Kerry these vets can't abide, but the smearing and slurring of American military men is the cause not that they served in Vietnam.
The vets were not welcome by the VFW because they didn't classify the Vietnam War as a war. When the first veterans did join, it was as Social members. My father was instrumental in our area of recognizing them. I remember when one particular soldier was killed. His parents were VFW members and my dad was the only member to show up.
Locally, I believe some of the WWII vets were afraid of losing their positions or status. Once they were recognized, they made some extraordinary changes to the local club and rose fast in the ranks.