> We collectively agreed long ago that monopolies do not get to enjoy the same freedoms that other companies do.

I think that's generally only the case for natural monopolies, such as power infrastructure, where breaking them up isn't really a feasible solution (ie we don't want 20 different power lines running to each house). I don't think payment processing meets that standard, we could easily break them up and re-introduce competition into the market.

Having a payment processing industry with a lot of competing providers would be miserable

Imagine having to support every single type of provider for every transaction. I don't think it is a good idea at all

a) One way or another, that's "not letting them enjoy the same freedoms as other companies"

b) How would you then prevent them from re-amalgamating the way Verizon and AT&T did after the Baby Bell breakup? Not just for a few years afterward, but ever?

c) I think that payment processors actually make a pretty convincing natural monopoly: consider that if we had 400 payment processors with no common interface protocol between them (and let's face it, without being forced to, companies aren't going to make such a standard), your Baby Visa #27 credit card wouldn't be accepted at a merchant who only accepts Baby Mastercard #100-200 cards. And even accepting that many different payment processors would be pretty onerous.

Remember, this isn't the card issuers we're talking about; this is the backend processors. The only reason our current "universal" credit card infrastructure works is because nearly everyone takes Mastercard and Visa, and most credit cards—and many debit cards—are either Mastercard or Visa. Sure, it would be possible to create some kind of an interchange standard that all 400 processors would follow, but again, where's the incentive for any single processor?