The WTC footage is documentation of a terrorist attack by innocent bystanders. The Christchurch Mosque shooting footage was created by the terrorist with the aim of becoming viral. It is a component of the terrorist attack itself.
Humans are largely visual creatures. If we don’t witness something, we have a tendency to treat it as less ‘real’. Doubly so when it happens half a world away: atrocities and their victims become almost theoretical.
Actually witnessing a video record changes our perception dramatically. The victims cease to be faceless ‘others’, and we receive a somber reminder that a maniac slaughtered husbands, wives, sons, and daughters—real people that could be your friends, family, or neighbors. The sense of tragedy and the casual brutality of it sinks in, and we are forced to acknowledge the evil among us.
In the U.S., where so many of these tech companies reside, we have become so bitterly polarized that many among us demonize nearly half our fellow countrymen on the basis of their political affiliations. At times like this, we could be coming together in our mutual disgust over this atrocity. Seeing it for ourselves is, perhaps, less important than seeing that those we condemn politically react with the same humanity that we do.
In a time when some people seem to honestly believe that “those [other half of the country] want to destroy everything everything I care about” we could use a reminder that, hey, we’re all people, and none of us deserve to die like that. And maybe then we could start working together to build a world that isn’t so conducive to hate.
All the talk about social media is just a distraction for the real issues that politicians don't want to face: gun laws. We probably shouldn't be selling crazy people weapons of mass destruction. But sure, blame Facebook for letting people post videos...
I'll also note that ISIS does a lot more editing and commentary to slant the content in their favor than this guy did. About all this guy did was make meme references... I can see an argument that this is quite different.
If it was an opinion-free, propaganda-free raw unedited video of a newsworthy event that was filmed in a public place, then it probably shouldn't be banned—though publishers should still act responsibly if the material contains deeply offensive or distressing material, or if it has serious privacy implications.
And that's just a proposed set of principles I came up with after three minutes of consideration—I'm sure with an extra 15 minutes we could come up with something even better. Point is, this isn't difficult. The fact that there are no bright clear lines doesn't preclude us as a society from drawing a line somewhere.