There's a wide chasm between good manners and legality. Don't get offended when your actions offend people. At best, it's hypocritical. Said differently: the legality of complaining about people being rude is already established. It isn't even slander/libel if you weren't actually rude, because being rude isn't a crime.

It's quite simple: Whitequark deleted the thread because there is a portion of users/readers on HN that are toxic and/or hostile. People don't want to deal with that type of traffic blowing up their Twitter notification feed.