Fraud? Abuse? Fine, let me put cash onto a card and if that card gets stolen, oh well, my loss. Mastercard should have no say in what what speech is considered acceptable outside of their offices. We don't care what execs at a water company think? Why do we care about the people at Mastercard?
If it were the case that the payment rail censorship were limited just to cases where there was an obvious elevated fraud risk-- then that would be the whole of the story. -- and there would be an obvious answer: use a payment mechanism where the fraud responsibility is entirely on the user, such as Bitcoin.
But their censorship exists where no such elevated fraud risk exists too, due to abusive conduct by the government to indirectly suppress activity that would be plainly unlawful for them to directly suppress. And the governments out of control abuse of its regulatory power is not limited to fraud-responsible payment rails, and get applied just as or even more extensively on Bitcoin payment processors.