So what is logically protected (pornographic) speech and what's obscenity? Not asking for an answer, just a thought to ponder. This isn't the first time this questions has been asked:
https://www.mtsu.edu/first-amendment/article/1004/obscenity-and-pornography
Regardless of how Elon chooses to proceed with handling it, the content at least needs to be better restricted. That's the most important (and perhaps easiest) way to start addressing it. Require a blue check verification for any account that chooses to upload that sort of material, for example. Also require age verification of accounts. This will solve many problems with access, and help curtail at least the illegal content.