I have experienced the self same dilemma when service at a restaurant is bad. I pretty much gave up and concluded it wasn’t a battle worth fighting cos there was no upside. You tip anyway there is no signal of bad service. You don’t tip you fit a stereotype.
I decided to tip anyhow and vote with my dollars by taking my business elsewhere if service turned out consistently bad — I tend to allow for the fact that any one can have a bad day at work for whatever reason.