It’s a horrible idea to close down 8chan. Those who were going to kill won’t stop because a website has gone down. But those who simply needed to vent now won’t have an outlet. It’s always better to have an outlet.
This whole idea that words (whether they are read online or heard from a politician) are so powerful that they make people murder and that words can transform reality in any way has deep religious roots but people are taking it way too seriously.
The need to respond to tragedy by shutting people up is pathological in itself. But searching for words that “created” violence is simply silly.