Since you seem unable to say "Fuck you!" to his or her face, then eat there one more time, say you're running away with a Russian cat circus, then walk away while shaking your head sadly.
If he or she knows where your business is, you'll have to rely on employees to run it, or, if you must show up there yourself: greasepaint moustache.
If they make you uncomfortable with that, mention something half-jokingly about it (while making sure to express how great the food is) and then reflect it in the tip. They'll get the hint.
If he or she knows where your business is, you'll have to rely on employees to run it, or, if you must show up there yourself: greasepaint moustache.