> The intent is obviously good, but you've given financial institutions the power to decide who can sell online.
No.
Financial institutions are bound by their agreements with the card associations, of whom you may have heard; one of their logos is on every card in your wallet. They, as private entities, have the prerogative under current US law to decide who may and may not use the payment rails they own, and this was the original genesis of rules disfavoring porn and other such relatively 'sketchy' businesses - not for moral reasons, or not overtly so, but for the high rate of expensive and complicated chargebacks those businesses generate. The associations can and do deny payment access to businesses or even institutions which generate too many chargebacks, and are thus forced to implement the associations' desires regardless of their own inclinations.
That's been true since long before the USA PATRIOT Act of 2001 gave rise to KYC/AML regulations in their modern form. If you want to argue against one or the other, you help yourself by ensuring you don't conflate them.
Meanwhile, if the description I gave of Visa and Mastercard sounds a lot like how Ma Bell could've been fairly described before a then much spryer Uncle Sam caught up to them, this is not by accident.