Editors must reject the Author-Reader agreement

Recognizing bumps in a manuscript is an essential part of having the editor's eye. It is very easy to get swept up in the language and implicit authority of the author and simply let him lead you. This is because readers are naturally inclined to regard authors as experts in a particular area. After all, didn't someone pay this person to put opinions between covers?
As a result, there are unspoken author-reader agreements, the most common of which goes something like this: As a reader I give you, the author, access to my brain, because I believe, implicitly or explicitly, that it will be more helpful to me to think your thoughts about a particular subject than it will be to think my own, or at least I want to use your thoughts as a place to start. (This is obviously a simple and very general comment about a complex subject, as fans of Mortimer Adler can attest.)
The editor's job is to respect the author's subject-matter expertise and insights, but to recognize that expertise is only one of several factors critical to creating a good book. An editor has to consciously set aside all author-reader agreements and try to be objective enough to recognize that, in almost every case (that I've come across, anyway), even though the author's work may be fine, or pretty good, or even perfectly satisfactory, if you are willing to think hard, be objective, and where necessary take it apart and put it back together, it can actually become far more helpful to the reader. It can become excellent.
Being in That Number
Our two youngest kids, ages 9 and 12, sing in a local community choir where they learn a lot of wonderful old songs that otherwise they might not be exposed to. One day we were all going somewhere in the car when they when they launched into When the Saints Go Marching In. At one point it started to die down so I tried to reinvigorate it by singing "Oh when the Day of Judgment comes...I want to be there in that number..."
They had no idea what I was singing and tried to tell me this was not part of the song. Do you realize what happens when you remove that verse? Suddenly an explicit limitation becomes an implied universality. The song becomes a celebration of everyone being "in that number." The excluded verse is politically incorrect because it implies, accurately, that before God not everyone is equal.
I remember even as a kid how that verse seemed to tie the package together. It was clearly central to the entire point of the song. There will be a number. Some will be in it. Others won't. That is the point of the song, and the truth and the tragedy of the fall.