Remove them from Google searches, de-platform them from the App Store and cut their access to hosting services.
They have failed to moderate their platform, in fact in this case it seems they did on the contrary, so it is only just they get their part of punishment.
Parler didn't get TOS'd because they had things fall through their moderation process; they got TOS'd because they did not have a workable moderation process in place, period. Twitter obviously does make mistakes - both AIs and humans are fallible - but they have about as good a moderation process in place as it's possible to have with the amount of message traffic they process.
Also, I'd like to point out that the only evidence WE'VE seen of this so far are a few claims made in a lawsuit.
Except it actually did have moderation, but it was leftists voices that were silenced.