You ever get that, at the vet? You're sitting there with your highly stressed terrified cat in her carrier, and some moron is letting his dog lunge and bark at the carrier. You turn your body trying to shield the carrier and the idiot says "Oh don't worry he's used to cats, loves them. We have two".
My response is to state "Well she ISN'T used to dogs and she's already stressed. Please take your dog away and make him stop barking".
For that I usually get a dirty look, while they might move the dog away, they still don't seem to get it.
Some might be gracious enough to say "oh I never thought of that".
I don't continue the conversation but if I did I would say "Never thought of it? Aren't your cats scared when you put them in a carrier and take them to the vet?"
(This rant is not based on a recent experience (though it does happen fairly frequently when I do go) because I haven't had to be at the vet lately. Something I read elsewhere made me think of it)