Re: Your "nutter on a rampage" is China's "Tiananmen Square"
This genie has long been out of the bottle. So there's the famous image of a protestor standing in front of a tank in Tiananmen Square. What happened next was available on rotten.com, a website I used to use to demonstrate why some restrictions/censorship is a good thing. 99.9% of us don't need to see the results because we can imagine them.
The problem I see now is there's often a knee-jerk rush to possibly exploit this kind of event. This article-
https://www.bbc.co.uk/news/technology-47583393
struck me due to some of the comments from political researchers, like this one-
"It may mean creating a special category for right-wing extremism, recognising that it has global reach and global networks."
Why make that special? Surely the best solution is to be able to monitor and act on extremism across the political spectrum. Language seems to have changed, so right-wing becomes 'alt-right', or 'extreme right'.. Which if you're viewing from a far-left perspective may seem logical. But there has been (and arguably is still) far-left extremism, eg anarchists, the Red Brigades, or even the Original IRA.
The BBC article suggests efforts have been focused on Islamic radicalisation, which is probably true. But hopefully some of the methods there can be applied to monitoring extremism across the spectrum, and being able to produce actionable intelligence. This particular nutjob had accomplices and would have left a digital trail. 'De-platforming' might seem like a good idea. Make the nasty go away! Ban 8chan! But that's always been an issue with censorship. Ban it and it'll just descend deeper into the 'dark web', making it hard to monitor. Extremist groups already use encrypted VPNs to try and hide their activity. I think there's also a risk that 'extreme' actions may also make people thing they're already being marginalised drift further towards the extreme sites.
To my mind, the best approach is a combination of clear legislation that defines extremism, which then can be used to enforce standards. Currently the issue is this nutjob violated 'social' media T&Cs, along with any human(e) decency standards.. But did the video break laws? It's news. It bleeds, it leads. Especially if you're the DM, who've never seemed too concerned about ethics or morals.
The hardest and possibly most controversial part is also probably the most effective, ie being able to monitor activity.. But we're generally opposed to the idea of a 'surveillance state' and the government 'spying' on us. But that's also the best way to try and identify, profile and catch nutjobs, hopefully before they act. But that's also a wicked problem. The Machine may be able to spew out a long list of people who've downloaded or shared this nutjob's 'manifesto', but how do you determine which of those people read it, and think 'This guy's right!'. I skimmed Anders Brevik's ramblings, and assume this nutjob's work is more of the same.