To expand on what you said - you can post some grotesque things here as long as you don't provoke flagging or offending the ~90th percentile into down-voting your comment in the first 24 hours, and language plays a big part in this, such as hiding bigotry behind big words and playing into confirmation bias. Low-level down-voting can be countered if you can get <1% of HNers, who may be fellow-travelers in the fringe ideology to vociferously agree & up-vote your comment.

I think this is a side-effect of HNs voting rules, what counts as "adding to the conversation", and the limited window for voting down comments and unlimited time to vote up.