How we cite our quotes: (Chapter.Paragraph)
Quote #4
The man was an impostor. Some low-born adventurer, masquerading as an oceanic grandee; yet so ignorant of the first requisites of mere gentlemanhood as to be betrayed into the present remarkable indecorum. (3.118)
Delano suspects that Don Benito is lying, but is totally wrong about everything else. Don Benito deceives him, but Delano also deceives himself. Note too that he thinks that Don Benito is lower class playing at being upper class, but can't imagine that the black people are free actors rather than slaves.
Quote #5
"It is now, master. Will master go into the cuddy?" (3.125)
This should surely be a tip-off; Babo says "master" but he's flat out ordering Benito around. Delano still doesn't get it though.
Quote #6
…the idea flashed across him, that possibly master and man, for some unknown purpose, were acting out, both in word and deed, nay to the very tremor of Don Benito's limbs, some juggling play before him." (3.270)
Delano sees that Babo and Benito are acting, but he can't see what they're acting. In fact, the very language he uses to describe them ("master and man") suggests the problem. He's incapable of seeing their positions reversed. Babo counts on that.