I see two issues with this. First: What you're describing is Gab - a platform that literally only enforces legal restrictions, the dynamic on that site is that

I see two issues with this. First: What you're describing is Gab - a platform that literally only enforces legal restrictions, the dynamic on that site is that the most extreme voices drive away the reasonable people that actually attract new people. Your rule would essentially also stop reddit from existing. The second is that Facebook doesn't have to censor you to censor you. They just tweak your post so it stops showing up other peoples feeds. Youtube does this all the time, they don't censor anyone, they just make sure no one can find the voices they don't like. Meanwhile the content they like gets boosted, we've seen this all the time where you go to youtube for a video about puppies and thanks to autoplay 4 hours later you're hearing about how feminists are destroying western civilization from within by Jordan Peterson.