There is a petition you can sign from ACLU if you are against Mastercard doing this to multiple sites with adult content https://action.aclu.org/petition/mastercard-sex-work-work-end-your-unjust-policy the aclu has a long history of help stop things like this with lawsuits and  persuading lawmakers like Scopes Trial ,Brown v. Board of Education, Roe v. Wade and Doe v. Bolton,

I want to say that I've been watching this petition since the takedowns on Steam and that before the takedowns on Itch it was ~75,000 signatures and now, as of writing this, it is over 116,000! ACLU does a lot of great work and is worth the time for a signature.

No legal organization can do anything to help if the effected parties just flop over and take it without a fight.