I'm not sure how well one can justify the claim that blocking social media is an effective means to prevent violence. As one example, people highlight the role that social media has played in religiously motivated violence in India. But violence has been worse without social media, no one can pin the blame for the 2002 Gujarat riots (perhaps better called a pogrom) on social media.

> So if the government knows that e.g. Henry Bemis is a known trouble-maker, it is easier to monitor his phonecalls, emails, SMS and find out what are his next steps of this bomber/terrorist/whatever. If Henry Bemis is using Signal, WhatsApp, Twitter DMs, Facebook messages, etc. it is easier to coordinate the next steps of an attack, awaken sleepers etc. without the government's security forces to be able to react equally fast.

So in other words, the elimination of social media's primary value lies not in the fact that it stops speech that calls for violence, but in the fact that it enhances the government's ability to conduct population-wide surveillance. So your underlying point is that better government surveillance is what stops violence, and elimination of social media serves to enhance government surveillance.

This might apply to "traditional" terrorism, that is centrally organized and coordinated. This is however not how most terrorism seems to work these days. Instead, we have something that's been called "stochastic terrorism". Messages calling for violence are spread by people, perhaps deliberately in the hope of someone acting upon them. Given a large enough reach of the message and enough people willing to commit these acts, this quickly becomes something incredibly hard to fight. I'm not sure about it's efficacy, but turning off social media is certainly not a completely invalid way to attempt to prevent more of that happening.

If preventing "stochastic terrorism" was the reason they turned off social media, shouldn't they have done it before the bombs exploded, possibly even before any of the terrorists used it, and not afterwards?

The multiple bombings that occurred in Sri Lanka hardly seem "stochastic".

Terrorism doesn't require hidden communication channels. But it is actually propaganda, usually foreign, so governments feel threatened by it and naturally want to block it. If they can't, they can decide to block the next best thing, i.e. uncontrollable mass communication channels. Censorship in its pure form, not counter terrorism.

In the cases of events, e.g. bombing a church, paramedics, firemen are easy targets/sitting ducks. Being able to block coordination of further attacks is important. The hidden channels is not to silence the propaganda. That will never happen. But communicating to a vast network of perpetrators that "I just saw the army driving to location ABC, therefore we do the round 2 attack in location XYZ".

I am never in favor of censorship. I am merely stating that I understand a potential use under these circumstances. I don't agree. I just undertand the reasoning.

You are not describing a terror attack then. The point of terrorism is propaganda.

I’m not for what they did, but this comment is to expand your idea.

You forgot to think about the people they don’t know about right now. I’m presuming they’re freaking the F out right now and are worried about unknown cells and their communications.

So... in the moment, decision was to make unknown cells communications more difficult by disabling low hanging fruit.

So should we, say, ban encryption or at the very least online messaging applications that offer end-to-end encryption because someone might use it for "something bad", or to hide something from the government, all this in the name of fighting against terrorism?