Need some help on GI mistreatment during the Vietnam War

I am researching a book on the Vietnam Antiwar movement and it's mistreatment of Vets. I have a large body of information that will probably surprise a few and not make those who participated in the Vietnam Antiwar movement happy.
The last piece of this puzzle is what is now termed the spitting MYTH. I have a huge amount of information from the war years that proves the spitting was KNOWN about and reported. There are a large number of reliable reports from those who were spit on. So far, I can find no records of any of these incidents. I mean nothing either way. Working in the San Francisco area, the police have no records pro or con. The courts say the records are "Closed" an dthey won't even look.

The problem is: everyone I talked to says the "spitting on vets" is a myth but they offer less proof than the vets who say they were spit on. If it didn't happen, just let me talk to a security guard or SF police officer that wants to go on the record that it never happened. There were people working in the airports yet not one has come forward to say I was there, it didn't happen.
If someone has a piece of paperwork, some incident report anything to document this, I really want to see this.
Anyone know of military records or documents that they might still have onthis issue? Example: an instruction sheet warning of the spitters. Directions to people traveling how to handle the situation if accosted. Anyone file a report at their next base?
I want to make this clear: the GIs all knew about this and it was COMMON Knowledge which was reported as such. Someone out there knows something and it is not hard to prove a negative: it just takes some work. The logs at SF airport would prove one way or the other what was happening. SO would the arrest reports, court records etc. No one in San Francisco has offered these for review....