Read the whole post as a unit, and realize he's telling him to STFU. He's also hiding behind this man's manager. He assumes the manager would also tell him to STFU, when in fact the manager would probably not have done that. In fact, the manager didn't do that.

The manager may have wanted to do that, although that is purely conjectures, but the manager didn't, perhaps because it's against company policy, but also perhaps because his manager didn't want to go all out on Michael, perhaps realizing that the faults in the matter might not have all been on Michael's side.

So, then, I think Googler123 is telling Michael to STFU not by telling him directly, but by putting words in his manager's mouth, which is I think even worse, because not only is this denigrating to Michael, but also to his former manager, who may still be a Google employee.

Makes sense?