The issue isn’t about who exposed him; it’s about what he posted online. His online activity provided the ‘context’ that led to scrutiny of his actions within Microsoft.

For example, he openly celebrated the burning of the U.S. flag in support of Palestine while working for an American company. The relevant context here is that any HR department in the U.S. would be concerned about the risk of him organizing a vigil on Microsoft property and potentially staging a similar stunt, which he might then share online.