I am so sorry that you were treated this rudely. It is totally uncalled for. Please know that the rest of us riders REALLY appreciate the effort you go through to provide the support to these events.
However, I have also volunteered and found this is the case with a few of the riders. I had to keep stating "sorry, your horse is not down, I don't care what your HR monitor says". I was taught early on in the sport, NEVER argue with P&R person or the vet.
Lee
"... And God took a handful of southerly wind, blew his breath over it and created the horse..."