Why shouldn't a store get to decide the $protected_class of which customers it will do business with?

Long term, I can imagine this becoming a corollary to Net Neutrality. Whenever that finally becomes a thing, the next step could be a law/rule that "public web sites need to be accessible by the public". Not that developers need to test their work in dozens of different browsers, but that they can't actively choose their customers.

In principle? Of course. I mean I remember blocking Yandex bots from hammering some e-commerce site on shoestring budget.

But each person developing a web scrapping bot realizes at most after a week that being honest with User-agent has negative impact on how well it works, and changing it to existing browser takes literally seconds.