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?
It's an important distinction to make. Credit is very much not something you should feel entitled to and issuer can and should be selective about who and what they issue credit for. Or course the credit industry itself is disgusting, but that's another issue (this was covered almost 20 years ago in a documentary Maxed Out).
This shouldn't be conflated with payments in general which is (imo) a much bigger problem. You should be entitled to spend the money you earn on exactly what you want, and to do it anonymously.
You can fight back: don't spend on credit and refuse to use a card when cash would suffice. We are losing, though. For stuff like Steam you have no other option (as far as I know).