[fostermom]

We had taken my male to Cornell U. and the intern was poking and prodding...Reno stood quietly through all of it until the intern started yanking on his leg...I saw Reno's lip curl, figured he'd had enough, and told the student to stop...in the six subsequent years we've had him, Reno has been nothing but an angel, including the vets.
Two of my fosters have had issues with vets' offices. My little gsd/boxer, who was the SWEETEST dog and went to a novice home where they adore her, hated the vets. I had to pick her up to get her on the table and control her head as she would snap at them at every opportunity.
My 10 mo. old rotti foster would literally "freak out" (and I mean big time...struggling, jumping about...totally out of control!!!) at the vets once the actual exam started. He'd be all wiggle butt and kisses in the waiting room, even when the vet initially greeted him...he was so social with the vet that they looked shocked when I told them to muzzle him...course once the exam started, they understood why. He adopted to a family who is now doing advanced obedience with him...I get frequent emails from them telling me how wonderful he is.
Especially with a rescue dog, we don't know their prior experiences...and I'm sure if "bad" things happen every time a dog sees the vet, he understandably might decide he needs to express his displeasure.
I'm sure these vet tech constantly have to deal with grumbly dogs...can't understand why she reacted as she did.