DH got into an argument with DS16 over something petty and suddenly called him a "psychopath" as an insult. DS16 then got into another argument with him and said that the language he uses is unacceptable and shouldn't be used in any household. Instead of realising his mistake DH then proceeded to say I will have to start whipping you with a belt. What should I do? Is this common behaviour or completely unacceptable?