[candybar]

This is legally nonsensical - nothing about Section 230 precludes any further restriction on moderation by another entity. Section 230 is and has always been about the act of moderation not specifically creating liability for the carrier of user-generated content - nothing about Section 230 grants the publisher any specific right not to be subject to further moderation at another level.

The first amendment angle is a stronger argument, but unfortunately for X, it's also extremely weak and would require overriding decades of precedence and essentially create a crisis - there are far more onerous regulations in place that are still relied upon in a way that having them constitutionally challenged would be extremely damaging.