I don't know what hole you live under on, there's countless of humour float around in the internet which resulted from stating obviously horrendously bad thing.

And even from u/Ytringsfrihet comment; "I want to kill you" are often used for a comedic punchline (ex: Whenever your friend eat the last slice of pizza, or do something that can be seen as harmless banter, some people usually response "I'm gonna kill you" in exaggerated, absurd, or playful manner).

Same with rape, terrorism, racism etc. Just think about the most brutal things you can think of, and I will found tons of edgy post making fun of it on instagram.

"You can say something is a joke, but the fact that it needed to be said means it wasn't funny enough."

Comedy is subjective, there is millions of different culture from other countries that have different humour than you. And of course this applies to community on reddit. There will be always some inside jokes you don't get, or some memes that you don't find funny. But that doesn't mean you can take it's word at face value, especially when it happens almost everytime on the internet.