This vet is an idiot.
And do not take away his bowl and put your hand in there to take food. You got lucky on your first one. This is a great way to CAUSE food aggression.
If you give it to him, it's his. If you want to avoid food aggression, do things like trade up, toss treats into his bowl, feed by hand.
~The strength of one's opinion should not exceed their knowledge on the matter~