Earlier quoted context omitted.
I think you're agreeing with me -- what specifically are you saying I'm wrong about? My comment said exactly what I think you're saying -- that businesses are free to choose what to accept, by refusing to do business in the first place. (Or did you mean to reply to the same comment I was replying to?)
You said, "US bills say 'legal tender for all debts', which means it's illegal not to accept cash once a debt is incurred." This statement is incorrect.
Is it the word "illegal"? I mean, if a municipality or organization refuses cash for payment of debt... then they're just de-facto forgoing the debt, right? If they tried to bring the debtor to court to compel payment in non-cash form, the court would side with the debtor, no?
So perhaps not illegal but merely unenforceable? (But with the same consequence of it not happening in practice.)