That’s the same point: artists put stuff out where you can see it on the expectation that they’ll get paid. If you don’t want to keep your side of that bargain, you don’t have much standing to complain about being blocked.
If a physical shop decide their terms only allow the customers with a membership card to look at the window from outside but decide to not put curtains, those terms do not apply to bystanders who could see inside. Same when my neighbour is naked with all the lights on. If she doesn't want me to see her, she knows what to do.
If they don't like this, they can turn me away at the door. But they don't, they let me and I'm not signing any contracts with them, so fuck their rule.