I am so very sorry you and Parker had this horrible experience. I certainly hope that Parker suffered no lasting trama -- physical or mental. Sometimes when you are "in the moment" you are so shocked by the behavior of who those who claim to be professionals that thinking is muddled. Hindsight is always better, you can think of all those things you would of and could have done, but during the event, we do the best we can do.
Sending hugs to you both
I would definately file a complaint with the the proper authorities AND stage a peaceful demonstration out in front of this vet's office to let other poor unsuspecting pet parents know just what type of person this vet is. Maybe a personal ad in the local newspaper.....
good luck!