My dad is a Vietnam Vet with a recent brain injury accident. The VA won't treat him!! Why?! PLEASE HELP!!?

You need to contact your local VA medical network (hospital). I am a Vietnam vet and always assumed I did not qualify for VA assistance because none of my current medical conditions are service related. It turns out they don't have to be (although one of my conditions actually turned out to be). My brother-in-law, who is a Vietnam era vet, like your father he did not serve in country, had been getting treatments for a back condition sustained on the job (non-service related) and my sister nagged me into going to the VA for a check-up. I brought my DD-214 to prove I was a vet, and they never blinked an eye. I got service immediately. I do not see why your father would be denied VA help for his current problem. It will not be free, but the expense is relatively cheap in comparison to trying to pay for it yourself.