Earlier quoted context omitted.
Last time I checked both Visa and Mastercard have no problems being used to buy cigarettes or alcohol. I'd bet that orders of magnitude more people die because of cancer caused by cigarettes and in episodes of domestic violence or traffic accidents caused by alcohol abuse than the number of people assassinated by hit killers hired online and paid with credit cards.
I never claimed the near monopoly of current processors is moral. My claim is easy: we have the right to conduct a business according to our ethics.
So at this point we agree (as a society at least) that some businesses should not be allowed to conduct business according to their ethics, but instead must do business with anyone who shows up at their door. At this point it's just a matter of deciding which businesses that rule should apply to. I would argue that payment processors are approaching utility-like levels of essential use in our society, if they aren't there already.