Visa and Mastercard basically have a monopoly on the market. To not accept Mastercard would do orders of magnitude more damage to your business than the impact your protest of not accepting them would have. It's completely unrealisitic to present that as a sensible option.
> is nothing but a business-hostile dishonest shakedown.
From the Guardian:
“MasterCard charged billions of pounds of unlawfully high fees for its sole benefit and to the detriment of consumers. It has already been found to have broken competition law, the basis of which was to protect consumers, and that cannot be disputed. There is no basis upon which MasterCard can contend that its card fees were not unlawful.”
So actually, Mastercard are the ones being business-hostile here.
A law is not fair if there is no way for a reasonable actor to know whether their actions are legal or not. It's especially unfair when something is seemingly fine for 20 years but suddenly becomes not fine and the government wants to confiscate retroactively. This isn't some ongoing wrongdoing that was only recently discovered; MasterCard had this arrangement with probably hundreds of thousands of companies for decades.