In macbeth. act 2 sc. 3, lines 85–90: how is the theme of guilt refined in these lines?

In these lines, Macbeth explains his "fury" upon seeing the murder of Duncan. This fury led him to kill the guards.

He says that it was not possible for him to be wise, confused, calm, and furious all at once. He could not be both loyal and neutral. In that moment, his rage at finding Duncan so brutally murdered prevented him from thinking rationally. Therefore, he murdered the murderers immediately.

Of course, Macbeth is not being entirely honest. He murdered the guards so that the real murderer would not be caught. But this speech does add an interesting layer to his mindset at this time. 

The sight of Duncan's mutilated body moved Macbeth to confusion and violence. He is correct in saying that rage prevented him from thinking rationally and reasonably. Macbeth's guilt over his actions has led to a troubled mind.