A Tip or Tips originally came from "To Insure Proper Service" I cant say that being insulted is proper service. And again you do expect something for your Tip, a better drink next time or a consistent drink and fast service. Not insults.
There is no doubt that the patrons of that eatery were cheated out of their gratuity by the stealth insults.
I'd take my business somewhere else where I would not be cheated. But not until I had some fun with that eatery though. :)