Is it "really important that people do not self censor"?
There are many examples of it being a desirable behavior, even unavoidable. Interacting respectfully with people sometimes demands it.
It sounds like some people demand being allowed to say whatever without fear of negative consequences. It sound like demanding that others do not set up minimum conditions for interacting, which is abusive in itself and sets the stage for future abuse.
Some people would benefit from shutting up. Their opinions are horrible and the fact that they do not realize it just makes it worse. Telling them to shut up is actually an act of grace.