For one thing, it's easy to say 'well we'd only take down illegal content'. But in practice there isn't such a bright line, there's lots of borderline stuff, authorities could rule something posted on your site illegal after the fact- lots of these situations are up to a prosecutor's judgement call. Would you risk jail to push the boundaries? Coordinating 1/6 wasn't necessarily illegal until- it was.
If Islamic State is recruiting on Free Speech Drive, posting manifestos, encouraging Western residents to actual jihad- you wouldn't take that down? You'd leave it up if it hewed up to the line of being legal- really? Jailbait or non-nude pics of someone's teenage daughter, hosted in the thousands- you wouldn't take that down? It's easy to be an absolutist in an Internet argument, it's much harder when you face the sort of everyday content moderation issues you see in the real world