This does matter. If it’s government, that is reducing free expression. If it’s private entities, it’s not. The government controlling what Twitter can or can’t disallow would reduce free expression (most notably, Twitter’s).
The solution here is utilizing public pressure to advocate disallowing the really, really bad stuff (i.e. pushing for genocide, advocating abusing children, advocating violence, etc.), but allowing real discussion. And for the most part, that’s what’s happening, though Twitter and others are falling short in some ways (and public pressure should continue to be utilized to put them on the right track).