Agreed. Myanmar has been at civil war since WWII. The Tatmadaw viewed Arakan muslims as enemies for decades before Facebook. In the 1980s they had policies against them. And that's just
one conflict in Myanmar. The Tatmadaw has been killing Shan, Karen, and other ethnic groups for 70 years. The Karen conflict is one of the longest running conflicts in the world. They're bombing Karen and Sagaing villages right now. Facebook is inconsequential to Myanmar's bloody politics.
It's true there are problems with Facebook. But without Facebook the Tatmadaw would still have laws against Rohingya, still have a policy of driving them out, still would engage in fighting ARSA, still would fund and promote groups like Ma Ba Tha, etc.