Modern online communities fracture into as many sub-groups as deemed necessary by both algorithms and user preference. Moving everyone to one platform won't limit the spread of violent hate speech, or limit organized sub-groups from co-ordinating violent activity.

From a platform perspective, there isn't much difference between companies curtailing the use of their platforms to carry out violent activity and those platforms curtailing other illegal activities such as spamming or malware distribution.

We don't consider sending 1 million unsolicited emails free speech, and wouldn't consider a gang using reddit to co-ordinate free speech. Is there any difference for groups coordinating the violent overthrow of an elected democracy?