Nah dude, you didn't get my drift. You said that instead of refusing service, you should spit in their food. I said that this would get you shut down by a health inspector. You said "they have to catch you", thereby advocating this method because it's hidden and no one will know you did it unless you get caught doing it.
The jump to mugging is intentional; the theory remains the same. It is hidden, and you only get outed if you get caught. Beyond that, it is about as useful as spitting in the person's food. Nothing is gained except self-serving satisfaction. You don't address the core of the problem, which is that person's public views and their public authority regarding those views. Refusing service tells them that their views are unwelcome (and civilized society should, ideally, agree on that point). Spitting in their food tells them... nothing. You spit in their food. Great. You'll smile while you watch them and then they'll take a private car back to the cameras where they'll peddle their abhorrent views some more completely unopposed without consequence.