I was an English literature major in graduate school, and at times like this my mind runs toward literary analogies. The bad guys in Hamlet make a plan to kill him and make it look like an accident. Their plan requires Hamlet to naively assume that a friendly duel will be on the up-and-up and not inspect the weapons for the planned deceit. They openly state that the plan will work because Hamlet is so scrupulously honest himself that he neither expects nor looks for deceit in others.
Similarly, In Melville's Billy Budd, the pure and innocent Billy Budd is shocked when he realizes the pure evil deceit of John Claggart, and he instinctively strikes out and kills him.
EDIT: I left out the moral of the story. Throughout my life I have generally trusted others to do the right thing for the most part, but because I have been burned so many times, that trust is eroding. When I am burned and see the treachery and deceit in others, I do tend to lash out in anger.