I live near a blue city in a blue state (I know, Hell) so it takes something of a monumental effort to not snap at these people when they get on me about not wearing a mask. Most employees are cool, but there's always one or two seemingly wherever I can go that have to make a big virtuous display of telling me to mask up.
I usually either say I'm good and keep walking, show them one in my pocket and then continue to not wear, or tell them I have a medical exemption.
How about you?
"I can't wear a mask."