my card has been "i have a medical condition". it's worked in some of the most liberal corners. didn't sport a mask once for example in Nantucket where they're not only liberal coonts but wealthy too so major attitudes of entitlement

i think it's all in the delivery. i look them straight in the eye in a very non confrontational manner and then turn away quickly while they're still thinking of what to say and now they'll have to pull an "excuse me sir but...."

on rare occasions they insist or they try to force me to some shithole corner of the restaurant, at which point i calmly take my business elsewhere.

the entire plandemic with the exception of flying on commercial airplanes I've been fine. even on planes I've got it figured out...bring lots and lots of little non filling snacks!