I don't think there's a way for Valve to avoid this. Like I don't think it would be enough to mark games as only available for purchase without support from the major payment processors/rails. Like disable those and add crypto payment support and only use those for those games. Those games being on the store that major payment processors support, they'll not want those on a store they support

This is a case where probably should be another store that doesn't use major payment processors but until alternative payment rails became popular, it'd be a low sales volume store. I know cryptocurrency has negative connotations because of the community, but I think those currencies are the only long term solution for people making porn games or whatever type of content that may have rich/powerful groups wanting to suppress