To your first point: the person could be wearing a mask because they see immunocompromised in some way, which would be a protected class (disability). You can’t refuse to serve someone because they’re disabled and wearing a mask as medical equipment to supplement their ability to move about in crowds, just like you can’t refuse to serve a person because they’re disabled and using a wheelchair as medical equipment to supplement their ability to move around in crowds. That’s a lawsuit waiting to happen.