Why not stop providing services if you cant scale the safety mechanisms that go with them? If it's hard to scale moderation in Burma, don't do wrap ups with Burmese mobile operators to put your service on everyones phone for free.
I'm not sure, but let me try to provide some reasons.
Firstly, Facebook (and the Internet in general) is used for hugely positive things in most people's lives. Stopping service would have a negative impact on most people. That might even include the Rohingya, who could use social media to organize for their own safety.
Secondly, it was not known beforehand that there was going to be a genocide, so the services were there at the same baseline as other countries and languages.
Once it's there and the people love it, I can imagine that taking it away would only push everyone to another platform. That might solve the problem for Facebook, but it wouldn't solve the problem for Myanmar. The article even mentions an alternate popular news site in Myanmar that also incites violence.
As for why provide services for free, are you suggesting that the people of Myanmar would be better off without free access to a subset of the Internet? I think their actions, and the actions of the developing world in general, speak differently.
If I remember correctly, Internet.org doesn't just provide Facebook access, they provide a handful of sites that include Facebook but also include Wikipedia and others.
>Secondly, it was not known beforehand that there was going to be a genocide, so the services were there at the same baseline as other countries and languages.
Except that Facebook employees were told directly that the country was on a path to genocide and Facebook was helping to fuel it. They had the warnings.
Between "do nothing" and "withdraw the service" there is a third option where Facebook does a good job moderating the platform so good effects are promoted and negative ones are limited. As the monopolistic operator subsidizing internet access for a majority of the population, they have a greater responsibility to avoid doing harm, and yet failed despite repeated warnings.
