I think that works only when you set those expectations up front. This is an apples-to-oranges comparison, but: reddit started as no filters. That was one of it's main draws. Then suddenly started applying filters, and banning "toxic" members. Now a lot of people are mad at them.

HN, afaik, has always had these rules in place. There's never been an expectation of free-speech here, and nobody minds, because they were presented up-front.