"Why can't the freaks on AO3 just go and make a site for all the gross stuff and leave AO3 alone."
Because AO3 is that site. Because AO3 was that site long before you decided AO3 was better than the sites you bullied us off of before, and I can promise you if someone somehow comes up with a fanfic site you like better specifically for the 'gross stuff' you'll try to bully us off that too so you can benefit from it.
AO3's specific core purpose is to preserve fanfiction, yes, but it was also instigated as a host site for the fanfiction that kept getting yeeted off other platforms like Wattpad. Its designed to preserve all fanfiction, not just the fanfiction you, personally, think is 'allowed' to be written.
AO3 is the site for all the gross stuff the freaks make. We've been there just as long as you. We've been funding it just as long as you have. AO3 has specifically said you have a place here. The timeline was literally:
Wattpad/FF.net/LiveJournal purge fanfics > AO3 is born > The people who's fics got purged moved over to AO3 > AO3 gains popularity as the best functioning site > The people who pushed for the fics to be purged off Wattpad move to AO3 > The same people try to push for AO3 to purge fics.
AO3's source coding is open-access. You go make a polished, strict, rigid site where nothing 'icky' is allowed. You go make a site where you can control what is hosted. We already have our space.
If you didn't know, the Organization for Transformative Works, the parent org to Archive of Our Own, is dedicated to protecting all fanworks. In fact, the Open Doors Project is a branch of the organization dedicated to archiving and preserving works that are at risk of being lost to time and purges.
AO3 was literally built to house the works other sites deem "undesirable," and continues to build halls for everyone.
There are a lot of great analyses of why censorship is bad . Early has a wonderful post about dark fic, ethics, and the fact that disgust is not an indication of morality. Censorship disproportionately impacts marginalized communities. Censorship based on some people being "allowed' to write and engage with certain content often requires painful disclosure to strangers which, again, disproportionately impacts marginalized communities.
