Ok, I can go with PART of that.
However, employees do not do things per the owner or manager(s) wishes or instructions, employees are lax, etc., all the time.
If a business posts “guests’ rules” of any kind, unless they were blatantly illegal or immoral (I have never seen such posted & would report such to law enforcement), I comply with them, or, if I don’t like them sufficiently, I leave. If I observe employees violating such posts, again, and especially if it would involve me in any way, I would leave. IMO, this is not a matter of “simple” property rights, it is a matter of FUNDAMENTAL property rights. Maybe it’s because I’ve done so much work closely in association with other small business owners, but I would not violate such rights unless it was, say, to save a life in imminent danger.
Now, if a grocery store, to use your example, publicly states that, in effect, customers can ignore the signs, THAT is different. Go for it, if you so desire. But you should at least respect other people and socially distance from anyone with a mask. For all you know, they are or take care of someone not likely to pass this life tomorrow, but still do have a high risk co-morbidity. And you have no way to know for sure if you are not a danger to them. (Yeah, I know, most cloth masks offer little protection against “incoming” but they may be doing the best they can, and may have little alternative to being “out”. Very few can shelter in place forever, and most people need to be out some just to preserve their sanity.)
If it bothered me much, I’d not just try “the phone”. One way or another, with persistence, small business owners and representatives of larger firms management can almost always be contacted. For ME, it is simply the wrong hill to die on. I am much more concerned that millions of livelihoods are being destroyed or have been. Like mine.
People will tire of masks, sooner or later. (Many already are, a double edge sword.) But if a huge slice of the small business community becomes dependent on the government teat, I’m not sure anything less than complete collapse of the country can undo that. Conservatism and freedom then just may as well throw in the towel and plan for the collapse.