It all rings very true to me: I think one thing to note is that not only did Facebook lack Burmese speakers internally, but so did the human rights groups with the best access to Facebook. As Kissane notes, Myanmar came online very quickly after the reforms, and -- unlike many countries in the Middle East or even China, because the story there was not one of authoritarian oppression, but a /release/ from authoritarian pressure, it did not fit easily into the template that tech companies were slowly learning to respond to. A few years before this, Facebook and Twitter had been shaken into some kind of recognition of their responsibilities in the Arab Spring and Iranian protests, but the result of that had been a very, shall we say, US-centric view of how repression plays out globally. Bluntly, the violent genocide of muslims by buddhists, in a country led by Nobel Peace Prize winner and defender of democracy Aung Sang Suu Shi, was a story that had to cut across many political and cultural presumptions of the US and Europe before it would be listened to.
I guess that brings me to your comment about "free speech". It seems a little petty to point you to the usual put-downs about how the phrase "shouting fire in a crowded theater" has historically been deployed to /silence/ people trying to /stop/ mass violence (because they are seen to be trouble-makers).
I'll note though that the failures of Facebook and others at this time came about because people claimed to be able to moderate and provide a forum where only civil discussion and "the truth" would be discussed -- and could be swayed to stop it, if you could just get through to the right people. Many of us, both in "free speech" organizations and on-the-ground humanitarian groups, argued that this was a role that Facebook was not, and could not play: and the more it claimed it could take on this responsibility, the more terrible the consequences would be.