Earlier quoted context omitted.
And if it's for human trafficking? Payment processors are made up of people, and people have to have the freedom of drawing a moral line they won't cross. The real problem as I see it is that payment processing is a near monopoly. Better competition and smaller players would almost guarantee that every transaction except the most egregious would have a willing payment processor. Diversity is so often the best answer…
How do you know it's for human trafficking? Are you deputized by the government to act as judge and jury? If you think something might be for human trafficking, you report it to law enforcement and let them deal with it. They'll gather evidence, build a case, make arrests, and hand things off to a DA/prosecutor who will file charges. Or, at some point, someone will decide it's not human trafficking, or at least that…
It's a thought experiment. There are surely cases in life in which you know for sure that crime is being committed. What you're asking for though is that due criminal process be a part of denying a payment. Which seems extremely heavy handed.
If my payment processing company doesn't want to help sell guns, or help with human trafficking, or hell, doesn't want to support the meat industry, then I should be able to run my business according to those ethical choices. My company isn't sending someone to jail. They are just refusing to accept a payment. There is no need for due criminal process to refuse a payment.
Should it be illegal to start a vegan payment processing company?