That’s an excellent point that should be fatal to venue. The official “X Terms of Service” clearly state:

The laws of the State of California, excluding its choice of law provisions, will govern these Terms and any dispute that arises between you and us. All disputes related to these Terms or the Services will be brought solely in the federal or state courts located in San Francisco County, California, United States, and you consent to personal jurisdiction and waive any objection as to inconvenient forum.

I have a hard time imagining that even the most biased court would refuse to apply X’s own plainly-worded forum selection clause against itself.