How does the boss handle such messages?

Ignore them, you have already said hello to the boss anyway. They can kick and scold if they want. When they are tired of kicking and scolding, they will naturally leave. If they kick hard, they will call the police. Next, your boss, after listening to your story, I personally think you are right. If the boss repeatedly accuses you and even doubts your quality as a person, then I suggest you think carefully about whether you are suitable to work in this unit.