I was only challenged once at the store, I never wear a mask. Just about every visit I am the only one in the store without one. It was a new greeter. I said - I have a medical exemption - and she said - ok you’re fine and folded like a cheap suit. By law they cannot ask you about your exemption according to the American Disabilities Act.
I just say I can't wear one. I haven't produced my 'medical exemption' card yet. CO2 causes my BP to spike. It probably does, getting angry usually manages that.
We have no choice but to go in the grocery store to get our nourishment or we will surely die from malnourishment because our restaurants won’t let us dine in. So we are held captive by their silly rules while the bullies in our society mouth off to their neighbor’s while hiding behind a mask. We are all living the same nightmare and we are going to have to fight back before the stores decide to deny our entry.