Steam suggests that 'Payment Processors cited Mastercard Rules'.
Itch.io suggests that Visa specifically sent them a note, but more importantly that Stripe forbids sexual content.
We need to be smarter about this. We cannot just let random Twitter and Reddit outrage memes control us.
Fortunately, Visa and MasterCard have been assholes to a large number of international folks so I'm kinda okay with this? But the controversy this past month on these sexy games is poorly researched in general IMO.
We are seeing big tech (Reddit and Twitter) flex their muscles and see how easy they can attack other companies. It's not even clear if the correct targets were chosen in this instance.
EDIT: my method of protest is to get a Discover (or AmEx if you prefer) so that we stop giving 3% of all of our commercial wealth to Visa or Mastercard. At least we can hit them in their revenue stream.
I don't believe that Discover or AmEx is big enough to seriously bully these organizations around. So there's safety in picking the distant 3rd and 4th place credit cards, just economically speaking.
There is also the fact that Discover has an alliance with JCB (Japans credit card) and RuPay (India) and UnionPay (China), meaning Discover is likely too weak to have gross international influence. (Relies upon local processors to get their card around the world).
Why? My research upon the Manga Library Z issue says that when Visa/Mastercard cut off Manga Library Z last year, both Discover and AmEx continues to support that controversial store. So that sets Visa/Mastercard as the troublesome ones, while Discover/AmEx might not have the strength to be troublesome yet.