I think we also have the obligation to not act as judge, jury, and executioner. If we suspect a customer has committed a crime, we should report that, with any evidence we have, to the proper authorities, and let them decide whether there's actually a crime there, or if we're mistaken.

Access to a reliable payments network (of which there are very few in the world, and even fewer in the western world) is required for doing any kind of online business. Whether or not to destroy a business based on their -- alleged! -- illegal activity should be decided by a court, not a corporate legal department.

Unfortunately, there are garbage laws around financial transactions that make MC liable if they don't do their own policing. IMO those laws need to go.