The Hollow Men all speak as one because they have the same identity: an empty one. The words "hollow," "empty," and "stuffed" are repeated again and again. Though we think we're dealing with flesh-and-blood people who happen to be passive and wishy-washy, in reality we're dealing with an empty void disguised as a person. The Hollow Men perform ritualistic actions like prayer and have some emotions, like fear. It's important to remember, though, that they are incapable of normal human reactions. They can't finish anything they start. Back on earth, they might have been famous politicians or journalists, but now they're just shells.
The Hollow Men represent people who are more comfortable taking part in a mob mentality than in holding their own moral viewpoints. They are the ultimate example of "groupthink."
The Hollow Men do not completely lack self-knowledge. They see enough of their own condition and flawed ideals to be ashamed of themselves. Otherwise, they would not be afraid to look at the "eyes."