The thing with physical public squares is that they are self-regulated - if someone commits a crime, everyone runs away and someone calls the cops, and the offender effectively has their life ruined due to a criminal record. If someone goes around and starts yelling hate crimes at people on the street, they tend to learn their lesson when enough people take notice and confront the individual with a warning to stop.

Unless you bring in real identities onto twitter, none of those societal protections will apply to social media. Nobody can do anything to spam/bot accounts if it's 1000 accounts being created every minute.