It would help to give some specific examples of threads or comments you think are hateful.
The more active HN users, with the support of the moderators, are quite vigilant about downvoting or flagging nasty comments.
Can you give any examples of nasty or mean comments that appear high up in the comment thread and/or without being faded or flagged?
The whole idea of Show HN is to encourage people to build interesting things and get feedback to help them improve their project and/or skills. So, constructive criticism should be welcomed whereas meanness should be weeded out any time it appears.
If you're seeing mean comments in Show HN posts, you should flag and downvote those comments and consider reporting them to the moderators at hn@ycombinator.com.