Born in 1980, so I was not around. But, I have read quite a bit of history, and have seen reports of that in multiple sources. I think that some, not all, of society wrongly directed their anger at the troops that were only following orders.
Edit: I did a quick Google search, and found this:
"Were you ever spat upon when you returned home to the United States?" asked syndicated columnist Greene of the Vietnam veterans among his readership. He received over 1000 letters in reply, many recounting specific details of just such a painfully remembered incident. Evidently this recollection of "hippies" (as they are often called in the letters) spitting on combat veterans has become one of the war's most unpleasant, enduring images. Conversely, other letters describe acts of generosity toward servicemen, from the typical free beers at the bar to a free show. But the over 200 letters excerpted here do more than confirm popular notions. They bring back the incidents of 20 years ago vividly, but not always with bitterness. And they reveal healing solidarity among veterans in response to what for many was not a happy homecoming. Recommended.
It's a review of a non-fiction book called "Homecoming: When the soldiers returned from Vietnam", by Bob Greene. Off of the Amazon site.