It's not exactly what he said. The fact the they agreed to a contract prohibiting them from using an outside payment method and then willfully violated that contract is a detail that courts may not be so willing to overlook.
Contract law allows you to sign away many rights you would otherwise retain. I'm not sure that a contract provision being found illegal under antitrust law has the effect of it being retroactively considered unconscionable or excuses agreeing to the contract in bad faith.