Apt analogy...

...for the way many Vietnam vets were coming home at that time.

They were "different" than their fathers before them who came home in victory from WWII. The sting of being protested as well as the thought they had fought and sacrificed for nothing no doubt was a big reason for the huge contrast between 1945 and the 60's-70's era vet.

Also, PTSD which had been with us from ages past, was still not understood. My dad used to call it "Shell Shock", so the mental damage that was done to many was not unnoticed; just no one knew what to do with the affected. Again, we came home victorious after WWII and with Vietnam men came home to nothing, with nothing, and made to feel deeply ashamed for their service instead of thanked and celebrated.

So Andy coming home withdrawn and later his dad saying "I went through it to but didn't come home like that!" was spot on for the sentiment at the time; regarding returning vets. (The scene with the mailman joking about what he experienced in Okinawa too was a sharp contrast to how 'nam vets seemed to feel. None of them were joking.)

The drug addiction aspect was spot on as well. Many vets came home with heroin habits picked up in Southeast Asia.

I have a feeling these topics at the time would not have been filmed had they not been dressed up in a "zombie" movie.