I really undersold the importance of MasterCard's shift in policy. I've not even had a chance to set up my laptop yet and since leaving Tucson to travel to Canada the situation has continued to escalate. To give you an idea of the problem, Visa and MasterCard are internationally speaking nearly absolute-authorities for bank funds interacting with E-Commerce platforms of any kind. If Visa banned all erotic and adult work from being paid for, no one would have any source of retaliation. The ACLU allegedly has been contacted to start looking at a case against MasterCard but we're talking about a Civil Suite that I doubt will get far. I don't think the ACLU could make a case here as in US Law circles it's a matter of private business. Internationally speaking, it's a matter of international law that the UN supported the minimization of payment processor options as part of anti-laundering operations.
The laws that handle this are why Crypto Exchanges are a failure, investigators can use the token data available on your typical Crypto Blockchain to identify end-users in transactions that attempt to cash out, making it poor for privacy. This also is why in the U.S. you can really only get pre-paid Visa's in Walmart (and some other stores, like Walgreens or Target) to use on Paypal as an alternative to having a bank account. Even then, Paypal may require you to have a bank account anyway if you want to take cash out of the account and it could just as easily deny you any payment if there's no identifiable information such as a phone # or other significant ID element. The Internet has gradually become entangled in the progressive and pervasive creep of making everyone [Named Persons], which adds accountability and liability to you in exchange for literally nothing but the privilege to do business. Anonymity has been dead, but this is sort of a final and chilling set of nails being hammered into the coffin.
*Note: I'm having a hard time finding some old articles I think my desktop at home has saved as bookmarks. Here is a 2010 FATF report that you might find relevant, it predates the policy changes that effectively secured Visa and MasterCard's Duopoly status (people will also note American Express is in the market, I wouldn't give that much debunk power given the state of affairs).
Ignore the warning signs at your own peril.
Edit: Helpful or adjacently relevant citations included as Hyperlinks, click on underlined text to see the citation for yourself. Turns out searching the internet in Canada is a little bit wonky, I can barely find useful information :/