"There is no argument of free speech here, they are a private business"

Constitutional rights are also civil rights - businesses may not violate them nilly-willy in this specific manner which causes damages to people.

You’re confusing constitutional rights with business obligations. The First Amendment restricts government actions, not private companies. Mastercard isn’t violating free speech by refusing to process certain payments. Civil rights laws protect against discrimination in specific categories like race or religion, not content moderation. Unless adult content is a protected class, your argument doesn’t apply.