Many years ago I had a vet that told me the same thing about my puppy. She then proceeded to show me how to correct the behavior by putting her hand over the pup's nose and squeezing her fingers into the sides of her mouth which made the poor thing scream in fear. By then 'I' was ready to bite the stupid woman but I was young and naive so I paid the bill and left. When I got home I called my mother sobbing and she said that vet sounded like a quack and to find another one. I filed a complaint with the vet's office and moved my records to another vet whom my pup loved instantly! So, unless you think your vet is correct and your baby is showing signs of aggression to you, I'd switch vets.
One thing that's worked well with my current 3 babies is I have always played 'doctor' with them - you know how you do with human babies - let me see your teeth, let me see your ears, etc. That way when they had someone else examining them it was no big thing
