That last part is pretty funny to me, now that you mention it.
I've kind of taken the other approach w/ stupid owners w/ nasty tempered little twits at the one vet clinic especially. I love telling my dogs as soon as I open the door (it's glass now, thankfully, so I can have some idea of what may be lurking) to "Leave It!" rather firmly and definitely loud enough that the stupid owner hears. Then I take a wide berth around the little (or big) nasty dog and if it comes toward us, I give that dog a body block and tell mine Good Leave It, Good Girl... and we proceed to the furthest seating from the nasty twit as possible. LOL. I think ever since this vet got aligned w/ a touchy feely behaviorist, temperament and manners have suffered. I have to tell the techs if they take mine for a blood draw in the back to Please tell them to Heel vs giving them a choice to go or stay. Drives me nuts.
Funny thing, the other vet clinic I use seem to have owners w/ pretty well behaved dogs. It's more of a "farm" vet.