It’s a good thing to be able to post the N word. If it is legal to do it why should X apply their own ethics on top? Thats how you get Reddit censorship

Because we decide on the quality of community, discussion, and engagement that we want to have, not the government.

HN has a lot of moderation just to keep this place a pleasant place to be. One of the most basic levers in that direction is to prohibit the worst slurs.