HN moderation is quite poor and very subjective. The guidelines are not the site rules, the rules are made up on the spot.
HN censors too. Facebook just does it automatically on a huge scale with no reasoning behind each censor.
Censorship is just tuning people or things you don't want out. Censorship of your own content as a user is extremely annoying and Facebook's censorhsip is quite unethical. It doesn't help safety of the users, it helps safety of the business.
Also Facebook censors things that are not objectively not offensive in lots of instances. YouTube too. Safety for their brand.