No one is required to do any work for an open source project, but they are expected to behave in a professional manner and plenty of people have been rightly criticized here when they acted inappropriately as part of an open source team.
Its debatable whether OP is right, but there's at least a case to be made that taking down documentation that was not costing any money to host for the sole purpose of making an unrelated statement (not one targeted at their customers, just society in general) does damage the professional reputation of the team and its product.
Anyway, if we ignore for now the circularity of that definition of "professional" and take it at face value, then swapping out your open-source docs for a political message would fail the definition of professional, not just based on the "earn a living" part, but also on the "specified professional activity" part. Assuming we're using their repo because it's, like, for programming computers and shit, we might be surprised to find out they had changed their profession from computer-programmer and computer-program-explainer, to worked-up self-important opinion-haver. Which even fewer people would pay money for, by the way.
Profession - "A professional is a member of a profession or any person who earns a living from a specified professional activity. "
If you want professional behavior, pay the person.
If you want free, you get whatever the person wants to give you for free.