The real question is whether or not the shooter who frequents 8chan/2chan/voat/etc would have committed the shooting if they didn’t frequent extremist sites?
And to your real question: its nothing different than saying movies and video games inspires a CRAZY PERSON to do harm. I can read 'Mein Kampf' without building gas chambers, and I'm sure you can too.
A separate site like Voat may be a bit different though. That is more of a closed ghetto for it.
It’s really ironic that given how much they bash it, the far right seem to be the ones who have taken postmodern nihilism the most seriously.