So you want AI censorship?
Hundreds of hours of video is uploaded to Youtube every minute, you can't have people to watch it through all. Twitter has thousands of tweets a second.
It's impossible to manually moderate social media platforms by your standard, it's the whole point of Section 230.
You remove disallowed content when it's discovered. Parler deletes illegal parleys when are notified, they deleted parleys from Lin Wood a few days ago.