You can make an argument about whether or not people should have thicker skin, but you can't make an argument that people should not be allowed to react to speech without forfeiting the moral concept of freedom of speech.
Someone did build the town square, and if that someone was a private entity, that someone can kick everyone right the heck out of the town square, because it's theirs. If the people of the town want to make that reality different, they should probably band together and purchase the town square and own it collectively, as a government.
If you think Twitch, Twitter, HN or Reddit are such critical infrastructure, then you should lobby your government to purchase them.
Homeless, poor, young and oddities get removed from malls for being themselves. We're seeing the same online.
Governments don't buy malls. Malls are designed to get you to spend. These sites want you to spend and if you do or don't they will send all of the info they collected about you and sell it to someone else.
We need more hobbiest sites. Government should provide free spaces.
Edit: someone built that town square. Someone founded those forums. At the end of the day, someone is always in control of something.