There are many places that do not even accept AmEx specifically because of their fees. Charging more based on card use has always been a thing until the card companies used their cartel like persuasion to not allow that. However, I'm starting to see stores offer different prices for cash/debit than credit. I thought I remembered this being made allowed again, but it's early still.

You as a user feel like you should be able to buy whatever whenever with whatever mode of payment. That's very convenient for you even though you're the one that has decided to use that particular mode of payment even though you know your mode of payment is an absolute pain in the arse for the merchant. Not having you as a customer is a perfectly valid point of view from the merchant.