The problem with that comparison seems to me that old public forums did engage in plenty of restrictions. if Facebook functioned like the Ecclesia, these rules would apply[1]

    Do keep to the subject being discussed.
    Do treat each subject separately.
    Do not address the same subject twice in the same day.
    Do not be insulting and invective towards a fellow citizen.
    Do avoid slandering a fellow citizen.
    Do not interrupt the proceedings by standing up or shouting or speaking on anything that is not in order.
    Do not lay hands on the presiding officers or interfere with their duties.

"The Board of Presidents were authorized to impose a fine of up to 50 drachmas* to anyone who violated the above rules." (that's about two months of salary).

In fact funnily enough the ancient Board of Presidents is really not that different from Facebook's community oversight board. You will not find any public assembly in history that did not enact rules of conduct and excluded offenders if necessary.

[1]https://studyingreece.edu.gr/7-rules-of-public-speaking-in-a...