In this section, Whitman describes his experience with all kinds of people and situations, as if to justify his claim to be the companion of all people.
He has seen everything from little kids to "suicides" that have just shot themselves.
The point seems to be that the world is a chaotic place filled with good and bad things, but still Whitman isn't going to judge anyone.
He's just an observer (see Section 4 and the "Me Myself").
He comes "again and again" to observe the seedy side of life, like crime and adultery.