If a Doxie were full sized, it would be pound for pound the baddest dog on the planet!
But they are not, and they respond well to discipline and training.
I have a big male(for a mini) named Barkley who is probably the most lovable animal I have ever owned. It is also the first small dog that I have owned.
He just met some small children for the first time this past Xmas(my Grandkids) and was absolutely on his best behavior.
What the vet experiences is the Doxies response to getting a shot or poked around. They are a bit snippy about stranger causing pain. So, I hold him and he does not retaliate.
Besides, most of it is just noise.(false bravado) But, they do have a righteous set of canine teeth.