Physical public spaces are regulated. Laws still apply there.

There are countless online spaces which operated like physical public spaces, where anything legal goes. Move off of the mainstream web and even the illegal stuff is allowed. You can literally run your own instance of whatever application on the Fediverse and follow whomever you want. No matter how radical or extremist your ideology is, someone will happily host it.

It's only a problem if one insists that all online spaces must be run under the same anarchic principles and must be forced to give anyone a platform, but that's far more dystopian than what we have now.